Depends on your favorite genre. Ps3 has some great exclusives in each category which are all pretty innovative. Here's my suggestions:
Rpg: Demon's souls(hard , but very rewarding)
Shooter: Killzone 2, MAG
Action: God of War 3( a bit gory though action packed and truly epic)
Adventure: Uncharted 2 (won many game of the year honors)
Puzzle : Heavy Rain (actually interactive storytelling but its , a great expierence)
Family: Little Big Planet (obvious choice)