RE5's most hyped feature--the new co-op--is what kills the game.
The game had a lot of things going for it. Graphics wise, this is astonishing, up there with Killzone 2. It also contains a lot of things RE fans would kill for, such as a fight with Wesker (woot) the origin of the T and G-Virus, and so on so forth. But then, it dies. Your foes are supposed to be injected with the T-Virus, but any RE vet knows thats crap.
The controls are identical to RE4, and thats a problem. When it came out, RE4's controls were great. They were easy to work with and felt good. But a generation has passed, and better games with better contols have come and gone, and Capcom has done nothing to address this. And enemies don't accommodate the slow control style. Some enemies are too fast to shoot, and in the end, but average game standards, they aren't even that fast.
Finally, the co-op. You wanna know how to kill a horror game all about isolation, with monsters everywhere? Throw an AI partner in. Even better? Make her incompetent and need to rescued every five seconds. Also, don't give her life--give her the most age old, basic dialogue ever and have her say it over and over and over and over...
Honestly, I wasn't happy about this game. Not at all. I was upset about how much of a deviation from the franchise this was. But I got my hopes up, convinced myself it wouldn't be as bad as it turned out.
If you don't understand, think of it this way--would you play Gears of War 3 if they gave it sluggish controls, terrible partner AI, and had him fighting regular humans instead of locust, with no real indication that 1 and 2 ever happened? Yeah, I thought so.