Playing this for the first time years after release just drives home the seismic impact it had on the genre. I don't think it's a stretch to say it's one of most important horror releases of the past decade, if not the most important. It goes so far beyond jump scares, tapping into a deep, primal sense of fear that overrides everything else and commands you to get out of this place as fast as you can. It's a high level panic brought on by the overwhelming sense that you're experiencing something that's wrong in some fundamental way. It's not just a smart, terrifying reinterpretation Sill Hill's themes, it's a horror landmark in its own right. The only other recent game I can think of that even comes close to this is Kitty Horrorshow's Anatomy.

(I played both Unreal P.T. and PT Emulation and I'd probably recommend Emulation if you have access to it. There's a lived-in griminess to it that suits the game, I think, while the Unreal version comes off as a little too clean in places. I know that's the more difficult version to get a hold of though, and I don't think there's a big enough difference between the two to warrant paying for one while the other is freely available.)