Poltergeist: probably the scariest PG movie I can think of. Compares favorably to many R-rated films.
Alien: I was 10-11 when it hit theaters (same weekend as Halloween), and knew it was a scary movie when I saw the fully posable action figure. I wanted it, but at $28, it would have been a big ask. And because I knew it would scare me in my darkened bedroom, I never did. When I finally got to see it, I thought it was brilliant.
Halloween: helped create a genre
Cabin In the Woods: I don’t think there’s a better meta-horror movie
The Thing (original): a great film that set a standard for many films that followed
The Thing (remake): a completely worthy remake
Invasion of the Body Snatchers (original): a great film that set a standard for many films that followed
Invasion of the Body Snatchers (remake): a completely worthy remake
I know that’s only 8, but I struggled narrowing it down at all, and there’s at least 20+ films vying for the last 2 slots…or replacing some I’ve listed.
There’s a bunch of Cthulhu Mythos stuff I’ve enjoyed. Sci-fi horror. Big-name classics.