My favorite is silent hill 2s soundtrack (I especially like "Theme of Laura").
While I won't make my judgement yet because I haven't played the games; from the nifty little horror playlist I assembled, Silent Hill 1 seems to take the cake.
I say Silent Hill 2 overall but my Fave Track is "Your Rain" off Silent Hill 4's soundtrack
2 it is! Very simple and beautiful arrangements. Soft but brutal, like getting hit over the head with a fur covered sledge hammer. And you can tell them that CFH said so.
I haven't heard the soundtracks to Origins or Homecoming, but from the ones I have heard i'd have to say silent hill 4. The one for 2 comes pretty close but I'm a sucker for the tracks with vocals on 4.
1 or 2, can't really decide! I love the retro-ness sounds of the first one cause they're dead creepy, but 2 has some unforgettable songs in.