I think RE5 looks more like a pure action game than anything else. It's not about the co-op, it's about the atmosphere. Everything that really made players want to play RE in the past isn't on this game.
Yes, RE4 lost a bit of "horror" but still, it's a Resident Evil game (the essence is there) but RE5 is just a pure action game with "Resident Evil" in the name.
For me:
RE1, 2 and 3= Suspense/Survival horror
RE4= Action/Survival Horror
RE5= Pure action game