Silent Hill is pretty much the benchmark of the genre. Well, the early games at least.
Always thought Resident Evil got that honor.
I've honestly never been a HUGE fan; the idea of "here are 5 bullets, make them last through 10 hours of gameplay" really, really annoyed me. Though I've heard good things about Alan Wake and considered re-visiting the genre.
I've been known to change my opinions on various media before given time between my initial exposure and then re-testing the waters.