Outlast
I was struggling about whether to recommend this. In many ways Outlast is amazing, but in some important ways it's awful.
Many games wear the "horror" tag without delivering the goods. Not Outlast. The story is horrific, the setting is horrific, the scenes are horrific, and most of it happens in almost complete darkness with the anxiety of batteries running out and monsters chasing you. My heart was pounding pretty much from beginning to end. Oh, and what a glorious ending that was! And the Whistleblower DLC is just as good, if not better. This is what the horror genre should be about. Classic.
But the description above already hints at one problem: pacing. The anxiety is relentless in its intensity. After a relatively quiet start in which you can take your time and explore your surroundings, things escalate quickly and don't stop. You're constantly running, if it's away from monsters or because you can see your battery slowly running out.
And so we get to the fatal flaw: an extremely annoying gameplay loop. It has only one shtick: chase sequences. There's some stealth involved, but it's optional and uninteresting. Do you find hide-and-seek to be a satisfying game? Because that's all you get here. What's so disappointing is that having too many chase scenes is the most common complaint for horror games. Not only did Outlast not get the memo, but the devs doubled down. And they're bad, repetitive chase scenes. Oh wait, there's also one more core gameplay element: trying to open the hundreds of doors that won't open. Thrilling stuff.
In summary, you're trapped in bad gameplay throughout the entire game.
This problem is exacerbated by a lack of diversity in level design. There are few awesome sequences but most of the game takes place in mazes of drab corridors and empty rooms. Turn left, turn right, it's all the same. In itself it would be bad enough, but when you add yet another monster chasing you through the maze ... not fun at all.
Play it if you're a hardcore horror fan but prepare yourself for a lot of frustration.