New horror movies suck! Everything is either based on schizophrenia or ghosts trying to communicate their domestic abuses to the living.

The Exorcist
-This will always be best horror. Specially the director version with the missing senses. This movie is based on a true, wait not like all the other horror movies claim, but real event of a boy's possession in the DC area of the US.

Other good ones are:

The Shining
-You can't go wrong with Stephen King and Stanley Kubric, two geniuses with a superb actor Jack Nicholson.

Night of the Living Dead
-It created it's own horror genre, how awesome is that!

Pet Sematary (1989)
-based on Stephen King novel, one of the best of his work.