Online CO-OP games

if your looking for co-op play where you have to interact and help your partner out to survive try army of two or gears of war 2

you could also try kaine and lynch

Left 4 Dead

Gears of War, GEars of War 2, Halo 3, Halo Wars, Army of Two, Left 4 Dead, Call of Duty World at War and Crackdown.vashkey

Me and my friend play Resident Evil 5 together over xbox live and we are wanting to get another game like it so if you have any good suggestions please say thank you very muchme0wmixx92

The upcoming Lost planet 2 will have 4 player co-op

left 4 dead

gears

g.r.a.w.

rainbow 6

fable 2(kinda)

Halo 3 is my favorite for co-op campaigns. 2 people on one TV, 2-4 online/system link. Different difficulties ramp up the enemies' skill. But if you want to spice it up, there are dozens of skulls that you can add to change the game up to make it more difficult, funny or wild. Not to mention the meta-game of campaign scoring. Turn that on and you guys are working co-op to survive, but competing for the most kills to get the highest score possible. Really, my favorite co-op game.

Another good one is Left 4 Dead, four people fighting wave after wave of zombies, but L4D only really shines with XBL.

Also, Gears 1 and 2 have great co-op. Gears 2 also has the Horde mode, 5 people fighting wave after wave of Locust.

Even though i really dislike the game, for Co-op experience, Halo 3 is a must. not only can you have four poeple playing at a time, the difficulty is scaled rather well for however ammount of players you have. Not only that, but the unlockable skulls help add variety to your experience (Although i can say when you are by yourself in single player, they seem to suck out the fun)

Another good game to do Co-op on is Saints Row 2. Its just plain fun going around and exploring the wide world of Stillwater with a friend by your side. and plus, you get to have dog fights : )