What makes a good horror film?

What makes a good horror film? And for those who don't like them: What makes horror films no good for you?

Gore. Lots of it.

Roger Corman's magic formula was horror with a little sex and a little humor sprinkled in.
It also helps if the victims are flawed in some way and deserve to die horribly.

Seen hundreds.
Most rehash the same old stuff.
An original plot, decent acting and good special effects get my vote.

Something supernatural but not overwhelmingly evil piques my interest. "Dark Water" was the sort of horror film I like.

I don't mind a good horror film, but can't watch anything 'torturous'. (Examples being 'Hostel' or any of the 'Saw' films). Quite like Werewolf films or things that make you jump.

Originally posted by FMF
What makes a good horror film? And for those who don't like them: What makes horror films no good for you?