Well, it's fair to say I've tried at least three other "MMOs": Disney's Toontown, Lord of the Rings Online, and Rappelz. 

Toontown was fun but silly, and I haven't played in years and years.

Rappelz was fun and interesting, but strange.  It's free - but if you want the good items and gear, you have to fork over a good deal of actual cash.  I didn't like the system, so I stopped playing.

Lord of the Rings I got to play the beta, before it was officially released, and while it was ok, I didn't like it enough to play it more.  It was kind of boring, the graphics were only so-so, and much of the animations annoyed me for some reason.  I assume it got better after beta, but in the end, honestly, I'm just not enough of a LOTR fan in the first place to really love it.