I don't really have a favorite genre, per se. I just like games that I don't have to think too much. Call me soft in the head, but I think all day; and sometimes I just want to check my brain at the door.
Some of the favorites are
Action
Run 'n' Gun
Platformers
Arcade type Beat 'Em Ups
FPS (Single Player Offline where no one has slept with my mom)
Sports games (Tiger Woods, NCAA Football, NBA)
I think that's it. I play pretty much anything other than strategy an RPG. I want to like RPGs, I just don't have the time. If I had 3 hours to myself a night, I might be able to play one.