The Haunting, the 1963 original, was the first movie that scared me stiff. Sure, by today's "horror" standards it isn't really that scary. But that's the thing about this movie; there are no jump scares, no excess of gore or violence. In fact, you don't see anything.
And that's why it scared me so much. My imagination was free to embellish all kinds of horrible possibilities for the things that happened in Hill House. And I really think that is what is missing from movies (and movie audiences) today, nothing is as terrifying as what our own minds can conjure for us.
I watch this every Halloween and it stills gives me cold shivers every time I watch it.