normally, when i talk about a good horror ANYTHING, i think that the most important thing is a good monster. whether it be IT, a predator, an eldritch abomination, or a human being, nothing's more terrifying than something you can't begin to understand. do ye know why predator's aren't scary? because now we know what they're society is like, and we understand them a bit, and they've lost all they're mystery. therefore, they aren't scary.
but, when you're talkin about a horror game,what truly makes them terrifying is when the rules in the game world are broken. when thing's you took for granted- enemies can't follow you into room's, you're safe in certain area's,certain enemies can't run- when these rule's are broken, that's when you're out of your comfort zone, and that's when it gets scary.
silent hill 2- when pyramid head- the guy who slowly drags his massive sword around- started SPRINTING after me, i feckin screamed. that's part of why silent hill is so scary- it's great at building atmosphere, and taking you out of your comfort zone. same thing with amnesia. other horror game's you should take a page from their books.