We can possibly debate whether or not X: The Man With The X-Ray Eyes is a horror movie. On the surface it's a scifi tale, but so is The Invisible Man, or even Frankenstein. But when you look at that trailer and see Ray Milland dance - how can you possibly say it's anything but horror?
Seriously though, X is a pretty great film, even without taking into account that it's a Corman movie. The dissolution of Milland's scientist lead puts the story firmly in the annals of great science run amok tales, and the ending is one of the most existentially disturbing finales ever. It could have been better; rumors have long persisted that the original ending of the movie had Milland, eyes gouged out, screaming 'I CAN STILL SEE!' Roger Corman has said he shot that ending, but didn't like it; it's never actually surfaced.
I don't normally advocate for remakes - especially of movies that I think are good anyway (and that star Don Rickles in a serious role) - but a new version of X with that ending complete... it could be good.