Darkness. Maybe not a terrifying movie, but its ambiance is really great.
Blair Witch Project (a classic imo)
Also, I wouldn't recommend Dead Silence. The acting, the story, the characters, and god that final plot twist are the worst...
If you're into it, Dario Argento's movies are nice too, but let's say they didn't age so well...
The Lady In Black has an amazing atmosphere and some really tense moments
Jacob's Ladder is an absolute masterpiece. Maybe not a "horror" movie, more like a psychological thriller, but if you like Silent Hill, you'll love it.
The Children is pretty neat, not great but it does the work. Also, you won't see children the same way anymore.
The Mist is great. Like, really great. And the ending is quite a punch in the face. Loved it.
And the last one I'd recommend is From Within. Not a masterpiece either, but it's a decent movie.
Just because you have an opinion doesn't mean you are necessarily right.
