@p ...it is true that the wave of slasher films started with Halloween, however the subgenre didn't have the legs of modern zombie films, which continue stumbling along to this day.

Also the crazy serial killer can be traced back to M with Peter Lorre, and the US version to Psycho. The gruesome R to X rated style is founded by Hershell Gordon Lewis with Blood Feast, then becomes art with The Texas Chainsaw Massacre.

Carpenter combined elements of serial killer, gore, the contemporary supernatural style of Rosemary's Baby and The Exorcist with what I think is the most powerful element - setting it where almost everyone lived in the 1970s - the suburbs.