1. To start with i think the obvious would be MAG. especilly if lots of people show up for it, and finally having a game night for PS3 again.
2. Also im not sure if you ever did anything for FIFA 10? so that if not.
3. And for Demon's souls, is all of the summoning/invading random? or can freinds be summoned/invaded? that would be awesome.
4. Apart from that it has to be Modern warfare 2 or KIllzone 2 or Uncharted 2.

Perhaps even do something a little older, like see who still has the skills on modern warfare 1 or world at war etc.