LoTRO: Great content, great concept, great crafting. But the gameplay was meh.
Age of Conan: System requirements were too ridiculously high. Loved the game, but the tech killed it for me.
WAR: Launch was fantastic. Questing was decent. RVR combat was insanely fun. But it didn't have staying power.
Aion: Actually played this quite a bit, pre-ordered and everything. I enjoyed the combat, but quests were lacking.
SWTOR: I have high hopes for this one. I'm big on character development and story, and I trust Bioware to pull it off. Also nice to get away from the fantasy world that every other game has been pushing.
A Pokémon MMO would still wipe the floor with any of the above + WoW, though.