I've recently been playing on the 360:
COD World at War: Nazi Zombies - Still impossible to beat after all this time
Warhammer 40000 Space Marine - Reminds me of Gears of War but more fun and less depressing
L.A Noire - Have been wanting to play this for a while but it's turned out to be quite boring so far
Left 4 Dead 2 -
Amazing!