+1
There is always a spotlight for the villain in any of these movies, so, really, you can take your pick. They've all got something going for them, especially those with 6+ sequels or incarnations. Freddy, Jason, Michael Myers, Dracula, etc., etc.--I certainly can't disagree with any of those choices.
But my vote for Greatest Horror Icon goes out to a character without whom none of these films--not to mention the notoriety of the iconic villains--would be possible:
The Idiot Victim
Ready to trip on a tree's root (or nothing at all) and crawl away from an advancing killer at a moment's notice, willing to leap out a second story window and somehow only suffer a twisted ankle in a single bound. There could be no body count without bodies, no terror without the terrorized--and that's where the Idiot Victim comes in, always doing the wrong thing at the wrong time to ensure that the film trundles on for at least an hour and a half, give or take. They give their blood--and, if a female I.V., often show their boobies--to give the killer something to do while the hero/heroine figures out how to stop said bad guy. And that's a sacrifice that needs to be acknowledged.
Idiot Victim, I salute you. You show me what not to do if I ever hear a noise outside (or in the basement, or attic, or... anywhere, actually) in the middle of the night.
__________________
You were a demon and a lawyer? Wow. Insert joke here."