Whose co-op is best?

Gamesrader goes and tests out the latest alphabet soup games Gears of War 2 (GoW2), Call of Duty: World at War (COD:W@W), Resistance 2 (RE2), Saints Row 2 (SR2), Left 4 Dead (L4D) and finally Fable 2 (F2). Who will survive a fight with your friends to the death? ZOMBIES that’s WHO!

I would like to get in on some Gears of War 2 action when it makes it way to the PC, Horde mode sounds fun. But I’m not sure it can beat Left 4 Dead in shear zombie awesomeness!