"Best Horror" is a tough list to compile - can't say I'd attempt it myself! - but I appreciate the effort (particularly the difficulties in rounding out 16-20!) Here's a link that may be of use, if you haven't already heard of Rue Morgue magazine: http://www.rue-morgue.com/
Cheers!
Okay, I can't navigate away from this list without noting one disagreement: Coppola's version of Dracula - top 20?!?
I loved Kilar's soundtrack, enjoyed Oldman's and Waits' performances and appreciated the faithful adaptation of Stoker's book. As an homage, yes, it worked - seeing classic fx and film techniques resurrected was a treat.
But: the casting didn't mesh (Reeves as Harker was a disaster!), the dialogue was so weak that it rivaled Godfather Pt. 3 and, between scene pacing and plot progression, the film's overall sense of timing felt so erratic as to induce nausea.
It could have been a great film had Coppola thought to draw on *his* strengths more, rather than deferring to Stoker's or various directors' work in the genre. As a period piece complete with lavish costumes and moody sets the film is credible and entertaining, but I can't say I think it merits any greater praise because it didn't contribute anything to the Dracula tale or the vampire genre that hadn't been done to death already.
(Now, If I may jump the rails of this particular train of thought, I'm glad to see that Martyrs made your list. Although uneven, it certainly didn't lack for ambition!)