I think the "scare factor" fo RE4 isn't goin to be "I wonder what's around the corner" like in traditional RE games, but more the feeling that you're being overwhelmed by a bunch of... things... that want to cause you harm. More frantic I guess you could say...
Either way, I love games that creep me out. ED was scary because of the story, and RE is just a personal favorite of mine, other than that I haven't really played any games that scared me. Killing stuff in Doom 3 was too much fun to be scary, and I thought the Silent Hill games were kind of boring. They had some bone chilling images and ideas, but nothing really freaked me out in those games. The new one has promise though, so I'll check it out if I can.