As a game in of itself, I'd say a B+. If it wasn't so linear, and didn't have so many QTEs, it would be an A+. Even if I'm bored to death with everything else though, I can always still play Mercs and have a good time. It's probably my current favourite game. It was the massive and constant story interruptions in the campaign that bothered me the most, and the story was only alright.
As a Resident Evil game, I'd give it C. In terms of the series it's just too off. I love the game, but I was really really excited for it and in the end wasn't really impressed as much as I expect to be from an RE game. Now I'm really really excited about Revelations (I only play console), and from what I've heard it's going to deliver more of what I'm used to from RE.