I'm guessing you'll play multiplats on 360 so just exclusives:
Out now:
MGS4 (can be played stealthy or heavy combat)
Resistance 2 (more arcadey then Killzone2, although for local co-op you may prefer R1)
Heavenly Sword (if you can get it cheap, it's short but similar in gameplay to GoW)
Notable mentions for the future:
Dead Souls (JRPG, available on import I believe, but you may want to wait for more reviews and info)
inFamous
Uncharted 2