You could probably put that title in the "duh" category pretty easily considering any game played via co-op is better than playing it alone. Am I right? Kotaku comes to us with some co-op experiences from playing the game at the recent Tokyo Game Expo. They basically say co-op is far more fun in this game than playing alone, although it does rely on some gimmick gameplay where you get across chasms together and they make an analogy to ICO with that.
They also want to stress that Resident Evil 5 should not be considered a "survivor horror" game and should be considered an "action game" like the author considers Resident Evil 4 to be.