tfishell: I was wondering if a religious or non-religious preference made certain kinds of horror scarier to people. I'm Christian (but also a shitposter and pessimist) but a denomination that doesn't believe in eternal hellfire/torture (which is pretty damn cruel :P), but since I do believe in the supernatural I find supernatural stuff creepier than people - many of whom I assume are atheist or agnostic - who think human beings are the ultimate things to be scared of.
I couldn't finish Doom 3 because it got too creepy for me towards the end - visuals, sound design, etc. I do owe Bethesda some money for it though, so if the original ever shows up on sale I'll pick it up.
I can't speak for all people, but I think most of us -- regardless of religion -- are desensitized to pop-fiction portrayals of hell and demons. They're just monsters, and we've seen them before. Even if you believe in fire-and-torture hell, having seen it all in games and movies probably means you take it for what it is, games and movies. Works of fiction. The same goes for cute little girls of course.
I think Doom 3 is scarier mainly for its atmosphere. But there's another theme that is common to horror: powerlessness. Now Doom 3 empowers you with a lot of firepower (versus rather unoffensive AI), but on the other hand, anything could spawn in (or sneak or jump out) any moment from any direction and it might be hard to see it in the dark. So things are constantly happening out of your control, and you're constantly on the defense, so to speak.
I don't really get that vibe from FEAR. You move forward into new areas, and there's new enemies to shoot. End of story. You're not constantly looking back left and right and trying to see whatever lurks or spawns before they attack you. You can take all the time to look around and crawl carefully, headshot the dudes you see, or turn on the godmode bullet time and slice through them like they're nothing. You're in full control, and even beyond.