I played Dead Space up to chapter 4 and didn't really get scared. I was a little scared of I think an instakill centrifuge, but that was only because it was instakill. Maybe I'm too much of a buzzkill though. Maybe I hate fun. But like, I link my experience to a game mostly to the gameplay, and when I have a cluster mine launcher and a heavily upgraded starting shotgun that two-shots enemies, I'm not exactly going to be easy to scare. Might make me jump, but the jumpier I am, the more likely a monster is going to get a bullet facial. If, say, I have no guns... then the game can possibly be scary.
Ooh, it also helps if the game has a good long time to build up an unsettling atmosphere. Even if I had a BFG, I'd be terrified.