RE5 is going to be the equivalent of a summer block buster. It's a must play.
I figure Silent Hill is going to be scary enough to actually frighten somebody to death! I'm not joking.
I pick RE5. As a game, I think it will be tough to beat. Silent Hill is going to be a hell of an experience, though. Even though I enjoy the tension, I normally have to force myself to play a Silent Hill game. That series is relentless with it's atmosphere.