I think the original Nightmare on Elm Street is really good; the only slasher/gore film that is actually scary. Freddy Krueger wasn’t seen too much, and was still a mystery. He LOOKED like a nightmare figure, and the story moved so that nightmare and waking was unpredictably but realistically mixed—with actual results.
A seldom mentioned movie that came out about the same time was Dreamscape (1984). Not quite as bloody but some gore, and every bit as nightmarish.
I like the classics, both the Hammer era and the black and white age of Universal Studios’ classics, but don’t find them scary enough for a horror effect.
The movies Insidious (the original) and The Conjuring, and The Ring are the only post-2000 horror movies that were scary imho,