Well there are many Split screen games.... but not so many cool ones recently. Currently i play left for dead 2, gears of war 2 and borderlands with my GF. There is a new Fifa every year... latest being the world cup one but not sure if its any good.
More recently i got lost planet.... but the split screen is shit... the second player has to play as a guest so no achievements for them and they will not be able to customize their character.