Even Jonathan Rosenbaum said something like "Val Lewton made noirish art films that people only think of as horror movies because the studios decided to market them that way." That's a paraphrase from memory, but I'm pretty confident that it's close enough.
After I watched the Paul Schrader Exorcist prequel, I read a bunch of reviews of it and a number of them said that it wasn't really a horror movie, even though it is a movie about a priest battling a demonic possession.
FWIW, I've never seen Rapture. I have seen Basket Case quite a few times though.