Heh, i've played DaoC, UO, Everquest, Lineage WWII online, Anarchy Online, beta tested earth and beyond, beta tested Eve online, star wars galaxies, and now I play Shadowbane. I had a hard time getting into most.. except UO and Shadowbane.
UO rocks

I had to quit because it was to addictive.
WWII online was fun as hell too, but my cd-key got pirated and became invalid.
Eve and Earth and beyond were just boring right up through final release.
Daoc was decent but tough to get into.
I didnt like EQ's interface at all and didn't get into it.
Shadowbane is a bunch of fun, and is meant for PVP. Lots of PVP in this one. I've played this one the longest probably.
Lineage was just cheap. Not so hot.
Everyone in Anarchy online was like lvl 200 by the time i joined, so i had to much catching up to do.
Star Wars Galaxies is the best looking of em all, but all the servers seem empty. Cant find many people on at once.