EDF 2017 is a must-play co-op shooter.
GRAW 1/2 has some co-op missions. Not a full campaign though (still fun though).
Rainbow Six Vegas is the same as GRAW 1/2. It does, however, have much more missions for co-op, as every mission is from the normal campaign + extra missions.
Marvel: Ultimate Alliance has GREAT offline co-op play. Yes, it's like the PS2/Xbox versions, with better graphics, but is very very fun.
You have all your great 2p sports games, if sports games are your thing. All the EA games are 2p, Forza 2 has arcade racing with 2p. TDU does as well, I think.
The Outfit (probably $9.99 new by now) has a 2 player offline/online co-op campaign. VERY fun combo shooter/RTS game. Certainly a good buy.
I'll think of more later.
Back from the dead, I'm afraid.
