1. World of Warcraft (TBC and early Wrath) - The raiding in TBC was the best around. Just grew bored when Blizz dumbed everything down. Been 2.5 years since I've played.
2. Rift - Was a great game but too much like WoW in every way. Lost interest, but am thinking of returning with their new lite model.
3. Warhammer Online - Loved the game but unfortunately the bugs and lag ruined the experience for me.
I've also played Aion, Lotro, swtor (obviously).