Doom and Doom 3...no way, never on my list I'm afraid, I was hugely disappointed by Doom 3 I'm afraid - too 'samey'. It started good in my opinion, it did have that scare factor, considering I have a dark monitor it became quite difficult to see the monsters, but after a while, it was far too repetitive in my opinion, the only sense of change was the fact the monsters got tougher, but you have a new gun by then. Didn't work for me...But I'm not saying all that I think about it, I don't write reviews for nothing you know, just go to Waza Online for Christ sake
Though I have played little Silent Hill, but I find they're a good bunch of horror games, ditto for Resident Evil and Dino Crisis. So probably Resident Evil 3 or Zero or Dino Crisis 2 (They should totally make a 3rd one).
I suppose American McGee's Alice scores for me too, some reason I like the idea of a child running around with a knife in a horror version of Alice in Wonderland, still haven't completed it though.
Look behind you a threeheaded monkey!