I don't have a complete favorite one either. It's between PS3 and XBOX 360 because PS3 has free online and some PS3 only games and XBOX 360 has better XBOX 360 exclusive games but you gotta buy xbox live.
Xbox360. Exclusive games like Halo 3, Gears of War 2, Fable 2. Online community (LIVE) and the command is so much better than the DualShock3 (to play FPS).