Roman Polanski's The Tenant remains one of the most frightening movies I've ever seen. It's a masterpiece of disorientation. Nothing is as it seems. The same can certainly be said about his Repulsion and to a large degree Rosemary's Baby.
These are my kind of horror(ific) pictures, I guess. Psycho, Cape Fear (1962), Misery, Near Dark, both versions of Invasion of The Body Snatchers, Candyman, A Stir of Echoes--the shocks are buttressed with a real concern for character and milieu. There are a lot of others I could have added to that list but unfortunately few of them have premiered in the past few years. I'm waiting for the next New Thing to take horror(ific) suspense in a different direction or to dazzle us alll over again with the old tropes all spiffed up.
What prompted this is a fine piece on the suspense films of Roman Polanski on Cinema Retro, a site you should put on your list.