Originally Posted by wolfing 
gameplay first! female NPCs with big boobs right after that!
Originally Posted by Zloth
Most important? Good folks to play with. I think that's the biggest reason behind WoW's continuing dominance. A lot of good friends will make even an awful game fun. No friends at all mean the game turns into a chore in 3 months or less even if it's an incredible game.
I forgot community. I like playing games with good folks, too.