I've never been a horror fan. I've never really been interested in Jason or Michael Myers or Freddy Krueger. The only reason I used to pick up the occasional Famous Monsters of Filmland was because I enjoyed the makeup effects side of things: the concepts and designs, the sculpting, the mould-making and casting, the painting and application of prosthetic pieces, etc.
For me, Alien '79's appeal has always been as science fiction. I don't class it as a horror film despite the fact that it has horrific elements to it—these things are merely the result of its science fictional premise. I feel the same way about The Thing and Predator.
OTOH, Event Horizon is the other way 'round; it IS a horror film, one that uses the trappings of science fiction to tell its story about supernatural biblical Hell. For this reason I don't have much interest in the film except for its technical craftsmanship.
The Exorcist, however, is a horror exception. I enjoy it because it's simply great filmmaking and great storytelling. Horror be damned.
Texas Chainsaw Massacre I've never sat down and actually watched, beginning to end. It has a certain credibility based purely on its historical notoriety, but that's about it. The same with Night of the Living Dead.
Horror per se, interests me not at all. But when the horror is there to flavour some other genre, notably science fiction, then it can work fantastically well.
Just my .02 cents.
TC