Besides it being a horror film and not science fiction or fantasy, I do agree about it being scary. Where we disagree is what makes it scary. For me, it is not the reveal, that I can handle. What scared me was not knowing what was down there. That was what I found scary.
I agree. DESCENT's reveal was well done, but the part where they first get lost was the scariest part of that movie to me, because it felt so plausible.
re: THE EXORCIST, I wasn't scared so much by the crab walk; but there's a scene where the mom is going up to check on Regan and the camera shows her completely dark room, and right before the door opens there's a nanosecond where you can see a devil's outline in the doorway. That freaked me out because I wasn't sure if I'd even really seen it.
Overall, that's a pretty good list. I especially like:
SIGNS: say what you want about the rest of the movie but that particular scene is amazing.
PEEPING TOM - I love that movie, more psychologically damaging than jump-scary.
THE THING - although "Clear!" - CHOMP! probably ranks higher for me.
I WALKED W/A ZOMBIE
MANCHURIAN CANDIDATE - hell yes
EVENT HORIZON - "Where we're going, we don't need eyes to see....
28 DAYS LATER
DAWN OF THE DEAD - poor, poor Roger
NOSFERATU - the whole thing, really.