Resident evil 1 (the music for part 2 is done well)
Silent hill 1 (2 and 3 blew)
Clocktower 1 (the sequels blew as well)
Doom : custom playstation edition (although nintendo 64's version had the most awesome ambience.. like monsters whaling echoing through the empty dark hallways)
The thing was good for ps2, but the movie was better
D was pretty good at scarefactor, dont know about D 2
AvP2 for pc is only scary if you play as a marine hehe
half-life is sci fi/survival I dont know about it having horror elements
my creepy moment was silent hill 1, where you're in a room with a bird cage, you hear wings flapping but no bird. Those little children with knives were scary as well as those yipping shadow children. I have to admit though, for silent hill 2, Pyramid head was sooooo scary as a character, especially when he's standing there looking at you through the bars.
I chose clocktower because thats the only game that I've played that acts like a horror movie. You hear him coming, you hide inside a box, a bathroom stall, a closet, under a bed etc. If you hide the same place more than once, he finds you and you have to press the panic button rapidly to dodge his razor scissors. One time I was investigating a room, and I looked into the fireplace and these hands came from above inside the fireplace and pulled me up and killed me. Another time a hand came out of a dresser drawer and started to choke me. I loved it all the way through *sigh* such a good game....