I gotta say , some of you get scared by strange games. Doom ? Fear ? Undying ? None of those games are scary , they are good games , but how are they scary ? Doom is one of the funest and coolest games i've ever played , but it's not a scary at all. Same for Doom 3 , there was all this oh it's [censored] scary hype around it and it was the least scary game i've ever played , in fact , i didnt even like it too much , i have to say i find the original doom much more fun and intense than the Doom 3 one. I LOVE resident evil as well , it's such a beautifull game to play(RE1,RE2,Veronica, Remake) , but again , not scary at all , just really really well done survival horror game. In fact Resident Evil was my favorite horror game, and one of my favorite games in general , untill I played Silent Hill that is. That was the first time a game actually made me nervous , I couldnt believe it. It;s still the only game that can make me uneasy , specially 1 and 3 , however , 2 is the best of them all , 2 is just a beautifull game , but not as scary as 1 and 3. I think a big reason why silent hill can get under ur skin is the combination of the music/atmospherics and the plot revolving around a cult , and "their" god , and other of this types of entities, after a while , all this together with the hellish place where your at , can actually instill fear in you , it's an incredibly well done game. For instance , take a look at who the last boss is
"Now this leads us to our villian - the one who's behind the whole thing. Sammael answers to many names such as Satan, Beelzebub and even Dragon. He is defined is the angel of poison or more familiar is his title of "the father of lies", given by Christianity. Children were sacrificed to Adramelech, a demon under Sammael's command in ancient times. What kind of poisons do we find in Silent Hill? Poison of the mind leading to insanity, poision of the body with White Claudia, poison of the truth which leads a determined father on a path of fear and deception. According to Jewish mysticism, in the legend of Talmud, Sammael meets another being cast out of Heaven by God. It is the demon, Lilith. (Remember the Lilith door in "Nowhere") Together, Sammael and Lilith are said to have each seduced Adam and Eve and the seductive serpent was Lilith, not Satan. His new companion becomes his wife and together they become a power couple of evil"
Silent hill is more than just a horror game , It has a lot of reference to real demons and angels , here i'll put some links to some pages that go more into detail on the references found in silent hill. Btw , if anyone reading hasnt played silent hill , definately read the pages , then find and play silent hill 1 or 3 , it's definately a completely diff experience than any other game u can play.

http://silent_hill6.tripod.com/id7.html
http://en.wikipedia.org/wiki/Samael

Those are a couple, there is a wealth of infromation on the subject on silent hill forums , I used to have some good links but this was years ago when i played the games. Definately Silent Hill is the scariest game i've ever played , and my favorite horror game.