Busy right now with Mass Effect 3 (could do some multiplayer I guess) but I also have: -Crackdown 1/2 (haven't beat 1 so I haven't moved on to 2. Would love to 100% 1 before moving to 2) -Halo: Reach (always up for some Firefight or whatever) -Left 4 Dead 2 (saw some of the 2 hour long video the podcast guys uploaded. Would love to actually finish L4D2 (got bored about halfway through it...something about playing by yourself seems to get boring after a while in that game), but I don't know about doing it in the hardest difficulty.
That's pretty much it for multiplayer games. Used to have much more but I traded the majority in because I didn't have anyone else to play them with.