So for early SCI1 releases, Sierra sold two separate packages: a 16-color (EGA) version and a 256-color (VGA) version. The EGA art was computer-drawn, but the VGA versions often used motion capture for animations, and scanned paintings for backgrounds.
Both releases were 320x200 res. Around 1992, when VGA became more commonplace, Sierra stopped making the effort of reproducing painted art in 16 colors. Instead, VGA versions of new games shipped with EGA drivers that rendered the 256-color art into a 640x400 16-color format.
The separate EGA releases of VGA games are rare in the US, and almost impossible to find anywhere else. To my knowledge, the games that had separate EGA and VGA packages were:
-King's Quest V
-Space Quest I remake
-Space Quest IV
-Police Quest III
-Leisure Suit Larry I remake
-Leisure Suit Larry V
-Heart of China
-Conquests of the Longbow
-Rise of the Dragon
-EcoQuest I
-Mixed-Up Fairy Tales
-and the non-adventures Castle of Dr. Brain, Jones in the Fast Lane, and Hoyle's Book of Games Vol. 3
Below are screenshots from Space Quest I, the icon version, and Space Quest IV in EGA and VGA. They serve as a good guideline for how these rare EGA versions looked as compared to the "normal" VGA releases.
As for why I chose Space Quest? For a long time, these were the only two of the Sierra "rare EGA releases" that I owned myself. A logical reason...
Also, be sure to visit a similar page that I made for Sierra's King's Quest V, as well as one concerning Conquests of the Longbow.
If some of the pictures fail to load, as sometimes happens, just refresh the page once or twice and they should be fine.
Screenshots from SQ1 remake:

EGA: Title screen

VGA. Actually, this is only part 1 of the three-part title. A waste of disk space if you ask me.

EGA: Opening credits. Hey, it's a Romulan Bird of Prey!

VGA. The 256-color credits have a cool "color cycling" effect that the 16-color credits don't.

EGA: the Deltaur forcibly docks with the spacelab Arcada

VGA.

EGA: Roger emerging from the Arcada janitor's closet

VGA: same scene

EGA: Roger walks through the Arcada electronic library

VGA. The relationship between Roger's EGA and VGA walking sprites is much closer here than in SQ4.

EGA: Roger uses the Arcada's data cartridge retrieval system

VGA: same scene, but a lot nicer-looking

EGA: What are you doing lounging around, Roger? You've got the cartridge; now get outta there!

VGA.

EGA: Roger in the room where the Star Generator used to be.

VGA.

EGA: the Arcada's bridge. Odd how it seems to be on the bottom of the ship...

VGA.

EGA: the escape pod control room, overlooking the pod bay.

VGA. I wonder what that gizmo on the right side of the screen does?

EGA: Escape pod airlock

VGA: Same here, too. Notice the Enterprise's console?

EGA: the escape pod bay

VGA. Hey, those stars remind me of Loom...

EGA: the view of the Arcada's escape pod bay from inside the pod cockpit

VGA. What sort of spaceship has just ONE one-person escape pod, by the way?

EGA: launching into warp speed for Kerona

VGA: same screen, different warp-drive effect.
There was a comic book adaptation of SQ1VGA, whose back cover featured the hyperspeed effect from the EGA version in VGA. Here is a scan:


EGA: the escape pod approaches the planet Kerona

VGA.

EGA: Long shot of Roger's escape pod in the Keronian desert

VGA.

EGA: Inside the ruined pod's cockpit. Notice the flat horizon?

VGA. Hey, there are mountains now.

EGA: Roger outside the crashed escape pod

VGA.

EGA: the wreckage of the pod, seen from a distance

VGA.

EGA: the giant skeleton of a long-dead creature

VGA.

EGA: the enormous skeleton, here shown in its entirety

VGA. Look carefully and you'll see the designers forgot to draw in the shaky spinal vertebra, leaving a gaping hole instead.

EGA: the Orat's cave is formed from what appears to be a giant dinosaur skull.

VGA.

EGA: Roger falls down a hidden elevator shaft

VGA.

EGA: the bottom of the shaft opens into a dark cavern

VGA.

EGA: a glowing force-field door bars the way forward

VGA.

EGA: the Two Guys comment on how badly Roger screwed up by plunging his arm into a vat of acid

VGA. SQ1VGA wasn't the only game at the time to joke about instant replays--remember the ending of The Secret of Monkey Island?
In the 256-color version the Two Guys' mouths are animated, but in the 16-color release they aren't.

EGA: the Slicing Dicing Laser Beams O' Doom (TM).

VGA: Sierra was fond of the laser-beam puzzle, it seems: there's one in King's Quest V too.

EGA: those acid drips are perilous... fortunately the NewRisingSun patches can be applied to SQ1EGA by deleting the file with "VGA" in its name from the zip.

VGA.

EGA: Roger gets turned into a human basketball by the Orat

VGA. I prefer the EGA version's death message illustration to this one.

EGA: our hero hides behind a rock as the Sarien Spider Droid and the Orat collide

VGA. I wonder why the Orat's right foot is posed differently in the two versions?

EGA: Roger drinks some of his water while crossing the perilous bridge of bone

VGA.

EGA: Roger returns to the eerie alien hologram with a gooey chunk of Orat

VGA.

EGA: the Keronian leader welcomes Roger and offers a skimmer

VGA.

EGA: inside the Keronians' compound

VGA.

EGA: the data cartridge, decrypted with the Keronian cartridge reader

VGA.

EGA: the skimmer minigame on the way to Ulence Flats

VGA.

EGA: the Rocket Bar in Ulence Flats

VGA: Roger looks at Roger, with humorous results.

EGA: getting a Keronian Ale in the Rocket Bar

VGA. ZZ Top's appearance in the game is normally censored; to see them, remove files "433.V56" and "533.V56" from your game directory.
WARNING: this will invalidate all save games made inside the bar.

EGA: winning money at the magnetized slot machine

VGA. Thank goodness the VGA version lets you bypass the trial-and-error gambling process in the original AGI game.

EGA: behind the bar. Just watch out for muggers, Roger...

VGA.

EGA: Tiny's Used Spaceship Lot

VGA.

EGA: the NAV-201 pilot droid

VGA. I guess the Two Guys got revenge for being sued by Toys-R-Us when they put in that familiar giraffe...

EGA: Roger considers buying the Drallion battle cruiser at Tiny's used spaceship lot

VGA. Although Tiny's a funny character, when it comes to pastiches of used-car salesmen, every adventure gamer thinks first and foremost of Stan.

EGA: Roger's timepod from SQ4 touches down in Tiny's parking lot.

VGA. Technically he should be landing next to Droids-B-Us, though.

EGA: another lightspeed tunnel of flashing colors

VGA. Strange how this warp-speed effect in the EGA version looks different from the one in the escape pod earlier.

EGA: the death message that pops up if Roger accepts his pilot droid's request to leave the Deltaur alone

VGA. Roger really shouldn't be wearing Sarien armor in this death message, considering he hasn't boarded the Deltaur yet.

EGA: floating in space, with the Deltaur nearby

VGA. Fortunately, Roger remembers to put on the jetpack himself... unlike in the parser version.

EGA: Roger outside the Deltaur's airlock door. Convenient how he got there without getting shot by all the nearby laser gun turrets.

VGA.

EGA: with the door opened, Roger tumbles into the airlock as his jetpack combusts. Waitaminute... combustion in a vacuum?

VGA. Maybe the air released from inside the airlock is allowing the fire to happen? Not that it matters... this is a comedic game, after all.

EGA: inside the airlock, Roger hides from the deadly cleaning droid

vGA.

EGA: the room just beyond the airlock

VGA.

EGA: the Deltaur's air ducts

VGA.

EGA: the Deltaur's laundry room

VGA.

EGA: the Sariens are all brawn and no brains

VGA.

EGA: Roger walks around the Deltaur disguised as a Sarien

VGA. It was oddly nice of Sierra to put a second chance to read the data cartridge into the VGA remake.

EGA: another Deltaur hallway

VGA. If they decorate their ship like this, the Sariens must have no taste whatsoever.

EGA: Roger in the Deltaur's armory

VGA. Hey, it's Marvin!

EGA: the Paranoid Android grudgingly agrees to fetch Roger a raygun

VGA.

EGA: with the Star Generator's forcefield deactivated, Roger can input the self-destruct command

VGA. That thing looks like a baby's milk bottle to me.

EGA: Roger unmasked in the Deltaur hallway

VGA. Lucky thing he's got that disintegrator pistol drawn.

EGA: stealing the captain's personal escape pod

VGA. The captain's choice of vehicle has style, I must say.

EGA: the Deltaur explodes

VGA. BOOOOOOOM!

EGA: the stolen Deltaur escape pod approaches Xenon

VGA.

EGA: Roger receives the Golden Mop for his services to Xenon

VGA.

EGA: a mysterious Xenonian with a faint resemblance to King Graham of Daventry congratulates Roger

VGA. Graham's face isn't normally that wrinkled, though...
Screenshots from Space Quest IV:

EGA: the standard Sierra logo for SCI1 EGA releases

VGA: a Sierra logo used in early SCI1 games

VGA CD: a shiny Sierra logo made especially for SQ4CD

EGA: the title logo, based on the original SQ1 box art

VGA disk version: this isn't really based on anything at all.

EGA: the game's subtitle

VGA disk version: the subtitle, with different colors.

VGA CD: the subtitle has had two ugly colored shadows added beneath it.

EGA: the opening credits

VGA disk version. How did they come up with the nickname "Two Guys from Andromeda" anyway?

EGA: the opening narration, and a shot of the planet Magmetheus

VGA disk version

EGA: the Sequel Police scan the planet for Roger's lifesign

VGA disk version

VGA CD: the crosshair animation has been redone

EGA: a Sequel Policeman interrupts Roger's retelling of SQ2

VGA disk version.

EGA: Outside the bar, two mysterious men eavesdrop on Roger's conversation with the Sequel Police

VGA disk version.

EGA: Roger comes face-to-face with Sludge Vohaul... er, face-to-hologram?

VGA disk version. Sludge looks a lot like a monkey, really.

EGA: Roger and Roger Jr. hide from the Sequel Police

VGA disk version: the same. Roger's face looks a lot better in the VGA picture, to me at least.

EGA: Roger Jr. prepares to open a time rip to SQ12

VGA disk version: same thing.

EGA: Roger falls through the time rip. It looks strange without the multicolored tunnel...

VGA disk version. Ah, that looks more familiar.

EGA: the streets of postwar Xenon from Space Quest 12

VGA disk version: there's some eerie red lighting behind the Super Computer dome

VGA CD: the dome is now more consistent with other views of it, but looks less dramatic

EGA: Vohaul's compound, seen from the devastated streets of Xenon

VGA disk version

EGA: Roger investigates a crashed landspeeder, formerly the property of a teenage farmboy.

VGA disk version: the dashboard close-up now shows debris and a cracked windshield.

VGA CD: the gray background has been repainted brown, and the close-up's border has been thickened.

EGA: "Be vewy, vewy quiet. I'm huntin' wabbits."

VGA disk version.

EGA: the rebels' underground base

VGA disk version

EGA: Roger unlocks the vault door leading to the city sewers

VGA disk version.

VGA CD: Roger's sprite has been redrawn here, making his jumpsuit darker.

EGA: Roger peeks out of a manhole at a Sequel Police ship

VGA disk version

EGA: Roger crosses the destroyed streets of Xenon to reach the patrol ship

VGA disk version. This is easy in the disk versions, but nigh impossible on the CD!

EGA: the Sequel Police ship turns out to be Roger's ticket out of the Xenon rubble

VGA disk version

EGA: the Sequel Police ship flies into the Super Computer dome

VGA disk version

EGA: the Super Computer landing bay

VGA disk version

EGA: Roger has an opportunity to steal a timepod

VGA disk version. The CD version plays the entire conversation before giving the player control, making the whole "sneaking" thing much harder.

EGA: Roger prepares to input a random time code.

VGA disk version

VGA CD. The CD version backgrounds have more color artifacts than the disk version ones; this is a particularly notable example.

EGA: traveling through time

VGA disk version: the same effect, with a palette shift added for a "time tunnel" illusion


Two images from the VGA CD: the dimensional wormhole is recolored to better match the rip Roger fell through in the intro

EGA: the Estros skyline as viewed from inside the timepod

VGA disk version: lots of yellow, which isn't as noticeable in the rest of the 256-color Estros backgrounds.

EGA: Roger on Estros

VGA CD: the same, but now Roger's eyes aren't visible anymore, swallowed up in a red blob of a face.

EGA: Roger in the talons of a gigantic pterodactyl

VGA disk version

EGA: the giant bird's nest

VGA disk version

EGA: captured by the Latex Babes of Estros

VGA disk version. The Babes look awfully pale here.

VGA CD. The Latex Babes' sprites have been recolored to look more realistic.

EGA: Zondra, leader of the Babes

VGA disk version

EGA: Zondra's submarine

VGA disk version

EGA: Roger looks around the Babes' fortress as he is marched inside

VGA disk version. If they're underwater, how come the windows are red?

VGA CD. Obviously someone at Sierra agreed with me, because now the windows are tinted blue.

EGA: the Babes strap Roger down and prepare to shave his legs off.
Incidentally, Zondra shouldn't be barefoot in this scene; that error was corrected in the VGA versions.

VGA: Zondra's eyes are miscolored here.

VGA CD: some minor details, including Zondra's strange eyes, are changed.

EGA: the cry of a sea slug interrupts Roger's torture session

VGA disk version

EGA: the Babes sound the cry to run, leaving Roger at the slug's mercy

VGA disk version

VGA CD. The slug's fins have been recolored, for some reason.

EGA: the slug stretches its twin tongues toward the trapped Roger

VGA disk version

VGA CD. Even the tongues have been fiddled with! Who was doing the art for this part of the game anyway?

EGA: Roger defeats the sea slug by making it choke on an oxygen tank

VGA disk version. Roger has really ugly legs!

VGA CD. That's better.

EGA: Zondra and Roger reconcile (even though from Rog's perspective, he hasn't broken up with Zondra yet!)

VGA disk version

VGA CD

EGA: Wilco Jr. is taken before Vohaul in the Super Computer

VGA disk: same scene, different dialogue line

EGA: the Galaxy Galleria shopping mall

VGA disk version.

EGA: Roger is deserted by the Babes the moment they set foot in the store

VGA disk version.

VGA CD: Roger's legs have been recolored to be more consistent with his overall skin tone.

EGA: Roger in the Big and Tall store

VGA: same scene, richer colors

EGA: the Big and Tall exterior. Not quite tall enough, it seems.

VGA disk version.

EGA: Roger walking in the Galaxy Galleria mall. Look, you can see his eye!

VGA CD. I wonder why Sierra's VGA animators were so averse to putting eyes on characters?

EGA: Radio Shock, without the icon bar blocking part of the screen

VGA disk version.

VGA CD: Hz. So Good shows up in place of Radio Shock.

EGA: the Monolith Burger exterior

VGA disk version.

EGA: the manager at Monolith Burger isn't very attractive... at least by human standards.

VGA disk version.

EGA: inside Software Excess

VGA disk version. On the floppy versions, the clerk will move his arms wildly when you talk to him;
on the CD, his face is seen in close-up, and his sprite's arms never move.

EGA: a parody of Brian Moriarty's Loom

VGA disk version. I certainly don't agree with this assessment of Loom myself.

EGA: Roger enters the Skate-O-Rama zero-g area

VGA disk version

VGA CD: Hz. So Good replaces Radio Shock

EGA: Roger floating around the top of the Skate-O-Rama dome

VGA disk version

EGA: the view of the arcade from inside the timepod

VGA disk version.

EGA: Roger in SQ1 Ulence Flats. Notice the shading on the buildings?

VGA disk version: The shading is gone! I guess that isn't really EGA in the VGA version after all.
Also, the disk version's icon bar fits under the game name, but on the CD the icons cover the "Space Quest ___" text completely.

VGA CD: the Monochrome Boys' bikes are now, fittingly, more monochromatic.

EGA: inside the bar from SQ1

VGA disk: A few small details are changed here, too. Check out the writing in the doorway, for one.

EGA: the Monochrome Boys complain about Roger's fancy 16 colors

VGA disk version. The reference to Roger's coloring has been updated; it was also changed on the Amiga to refer to 32 colors

EGA: the hallway leading inside the Super Computer, with the lasers disarmed

VGA disk version

EGA: Roger in the landing bay, just outside the laser-beam corridor

VGA disk version

EGA: the PocketPal laptop detects the movement of security droids

VGA disk version

EGA: Roger in the Super Computer's main control room

VGA disk version. I love what the artists did with the design of the computer's innards.

EGA: the Super Computer's Windows 3.1 interface

VGA disk version

EGA: Roger walks through the hallways unmolested by droids after setting the computer format sequence

VGA disk version

EGA: another eerie area inside the Super Computer maze

VGA disk version

EGA: Roger in the bowels of the Super Computer

VGA disk version.

EGA: Roger has knocked Vohaul (in his son's body) into the stasis beam

VGA disk version

EGA: Roger's inventory. That disk with Roger Jr. on it is an old Sierra floppy, from the days of SCI0 and before.

VGA disk: the disk is no longer identifiable as a Sierra release.

VGA CD: the floppy is now a "new style" Sierra floppy, used for pretty much all the company's VGA games.

EGA: Vohaul's mind-body transfer beam control panel

VGA disk version.

VGA CD.

EGA: Roger Jr. is restored to normal

VGA disk version

VGA CD. This version omits Roger Jr.'s line: "Thanks for saving me. I thought I was a goner." I have no idea why; it's in the game audio file.

EGA: a holopicture of Roger's future wife, Beatrice.

VGA disk version: the same as above.

VGA CD: slightly different from the disk version's picture

EGA: Roger and Roger Jr. shake hands

VGA disk version.

VGA CD: Roger's and Roger Jr.'s faces have been redrawn.

EGA: Roger Jr. sends his father back to the past... no, the present... never mind.

VGA disk version.