I wouldn't call myself much of a horror fan, because so many horror films are so predictable and/or trite that you can see them coming a mile off and/or they can't hold the suspense. As such I mostly prefer "sense of building unease in everyday surroundings" horror films of which I think all of the following have probably been mentioned already.
Rosemary's Baby - still as good as it ever was
Get Out - a few pointless jump scares is all that mars this one
The Wicker Man - had the ending spoiled for me by seeing Shallow Grave first, but that didn't mar my enjoyment of this film one iota.
Kill List
The Stepford Wives
Ring - sound design alone is terrifying
The Mist - "humans are the real monsters" shocker that's a massive improvement on the original Stephen King book thanks to some inspired casting (Marcia Gay Hayden as a religious bigot and Toby Jones as a shelf-stacking badass?!)
Perfect Blue - Satoshi Kon's manga about a would-be actress undergoing an identity crisis
The Lighthouse - could also be seen as a comedy TBH as it's two brilliant actors going completely over the top but it's got psychological horror seeping out of its pores. His previous film, The Witch, is another brilliant contender
Duel - Spielberg's classic evil truck driver
The Descent - more action-ey than meditative, but one of the vanishingly few films I've ever had to stop watching (I'm claustrophobic)
In the Mouth of Madness - rather shlocky Lovecraftian knock-off that's elevated out of the mediocre by Sam Neill
Event Horizon - another shlocky outing for Sam Neill, paired rather brilliantly against Laurence Fishburne and some of the most beautiful set design I've ever seen. I probably rate it higher than I should because it feels like a WH40K prequel.
But yes
Reno the original TV version of The Woman In Black is an absolute masterpiece and was one of those responsible for if not starting then cementing my love of the genre.
Along with The Signalman.
Another made for TV film that was part of the amazing Ghost Story for Christmas thing the beeb used to do so well.
It was a short story by Charles Dickens.
It has been, historically, when I have looked, been almost impossible or very expensive to get hold of on DVD
I'm lucky enough to have The Signalman on DVD (along with the rest of the ghost stories). It's a masterclass in dramatic tension based almost entirely on setting and a fantastic performance from Denholm Elliot. Network have, I believe, done a blu-ray remaster of the original Woman In Black which should be out shortly, I believe it hit some streaming service or other a few months back.