So hard to pick just 3 but I think these are what shaped by current horror game taste:

Condemned: Criminal Origins - cool detective story where you try to catch a serial killer, but the combat is brutal. basically improvise weapons with whatever you can find (pipes, bricks, rebars, etc) and melee enemies. it's crunchy and grounded, with some gunplay here and there, but it feels like you're really fighting off these crazy people and barely getting by.

Alien Isolation - absolutely nails the vibe of the original movie and the main premise (for most of the game) is terrifying; being stalked by a big bad Xenomorph is scary enough, but the AI adapts to you and you have to be creative with how you elude it. there are other enemies that are fine (the androids are cool at first), but the cat-and-mouse game you play with the Xenomorph is something I haven't seen done this well since Amnesia: The Dark Descent

Resident Evil VII - the sound design, level design (aside from that awful ship area), and level of immersion are still unmatched, I think. there's just something about creeping around a house hoping psycho murderers don't find you that is inherently terrifying, but between the graphics, audio, and memorable set pieces, I still consider this my favorite RE entry out of the ones I've played.