If we want to get in the way back machine, The Blob was the best of that time. It was the template for "there's something wrong here that can't be explained like missing people but since you're teenagers, the authorities can't believe you" movie. Another with that premise that was a kick in the pants was Killer Clowns From Outer Space.
And I like the premise of "it's not over" like Halloween left you with at the end. No one wants to admit it but everyone checked the back seat of their car at least twice after leaving that movie. You know he's not there and I know he's not there but does he know he's not there? Might just check a third time, can't be too careful.
I took my wife to see Halloween and after we got home, she followed me around the house, even stood outside the bathroom door talking to me about anything. I laughed and told her she was being a big sissy. But truth be told, if she hadn't been following me, I would have been following her. And would have gone into the bathroom, to hell with talking through the door.
I have a requirement for a movie to be horror, the monster or perp must be small enough to fit in the closet, behind the door or under the bed. Large monsters are more creature features and while I like them, they don't make me keep checking behind the couch.
