Guessed by @drbunnig
It's now been two years since I finished Alien: Isolation, and put it at #20 as a last second addition to this list. I wasn't fully sure of where to place it because of the lack of time to process it, but one thing I would've never expected back then was for the game to remarkably climb even higher on the list for two consecutive years after. I kind of assumed recency bias was playing a hand as it often does, but this game, man, holy shit.
I haven't even replayed it since then, though I have watched a few other playthroughs, most notably watched my best friend play through it about a month ago. I don't think I could be convinced into going through this hellish nightmare again, lol. I'm not exactly experienced in horror games, I've barely played any of them - my interest in this is mainly because of the Alien franchise - but I'm pretty sure even if I went on a marathon of playing through every famous and acclaimed horror game, I wouldn't find a single one that'd scare the living shit out of me like this did. And beyond just the scares of course, this stands right up there with the best works of the Alien franchise with its stunning aesthetics and vibes, and a story that ties into the movies in a great way even if it is rather basic. That Sigourney Weaver agreed to play a role in this because she thought it was ambitious and interesting should tell you everything you need to know really.
I'm still kinda shocked at the recent announcement of a sequel to this. I never thought it'd get one, and now I wonder if they mean a literal sequel that continues the events of this game's storyline, or just more of a new game that shares similar concepts. Either way, the people at Creative Assembly have showed that, even if they specialize in a different genre entirely, they sure know how to make a damn good Alien game. Isolation is the best thing to come out of the franchise since the 1980's, which maybe isn't a high bar, but it really is so special.