Phantasmagoria 2 is also a game quite unhealthy, and Dark Seed 1 & 2 with the pictures of H.R.Giger too.

This list is severely lacking in Thief and VTMB. It's already been said but the Shalebridge Cradle remains one of the best designed horror levels of all time. The Ocean House is a close second. The usage of negative space to create suspense has rarely been matched, and despite the fact that you barely encounter any enemies in either of those the sheer pacing and atmosphere makes both of them some of the most intense experiences you can have in video games

Clive Barkers Jericho - sick scary sh*t :D

Isn't that from Freespace 2 when you're almost rammed by one of those Satanas juggernauts?
But yeah, Freespace 2 was a pretty scary game in some ways, almost Lovecraftian...when you realize that the Shivans have dozens of those juggernauts and that your situation is pretty much hopeless.

Being suddenly, casually informed by the game, while looking down a blood-spattered hallway in Outlast, that you can look behind yourself while running by pressing Q and E...

(In case no one understands what I'm getting at: I was standing in a huge room with no enemies in sight, looking around and down the adjoining hallways, trying to figure out where to go next, when all of a sudden a game tip scrolls across the bottom of the screen, telling me I'm able to look behind myself if I want to as I'm running away from enemies! As in: hint hint, look behind you, sucka!

As it turns out, there was nothing there, but that game tip--that meta moment--creeped me the F out much more than any jump scare in the game itself did...)

How is METRO not on this list????

The rail cart ride early on, with the shadows in the tunnel... and everyone else slowly losing their minds... is one of the biggest WTF IS GOING ON moments in video game history. You don't know if you're dealing with ghosts or mutants or aliens or WTFever. That entire sequence..... the building horror, the gibbering passengers, then falling off, find the hiding spot as the animals race past, then making a mad dash for the gun emplacement.... good gawd the whole sequence is so expertly crafted. It's a thousand times scarier than any cheap jump scare could ever hope to be.

Alone in the Dark series is pretty hard to beat in terms of atmosphere and scares, etc. Plus its a classic.

Condemned: Criminal Origins, especially the school level, where you keep finding tidbits of Mr Tibbits.

wow true. Loved this one.

Scariest moment I ever faced in classic pc gaming was loosing my level 99 character in diablo 2 after not logging in for 90 days. I still wake up in cold sweats cause of that day, no lie...

I could add a few non scary games which scared me, well...one. Then I will mentioned 3 games I found truly scary and unnerving even today.

The first is the very first Test Drive game on my Atari ST, 1987 or thereabouts. Where? You are driving with a mountain wall on your right side, two lanes, and a cliff on the left side. You are driving at 150mph trying to get rid off the cops. There is a turn which you have to take or die and out of nowhere a lone station wagon appears coming towards you at 150+55mph, all in 1-2 frames per second. You can see the horror in their eyes.

The 3 other games.

3. Realms of the Haunting. Scary ass game with a great mix of fps, adventure and horror.

2. Necronomicon: The Dawning of Darkness. A pure point and click adventure game in first person view. The graphics, sound and overall feel of this game just creepy AF. I wish GOG would bring it here.

1. UFO Enemy Unknown on the PC. Soundblaster. Having your team of inexperienced troops with under-powered weapons, facing unknown monstrosities. Searching buildings, the barn to the left, what was that? A chryssalid! NOOO! Shoot it, bang bang! Nothing stops it....AAAAARRRGGH!
The music playing in the background, scaring you even more. How are we going to defend against these creatures?
If you manage to survive further down the story, you meet your first aliens who can take control over your troops. Getting attacked while suddenly losing your best soldier to a psychic attack. You can hear civilians screaming and dying, I can't help them, I CAN'T! NO!

Way too much to choose from