I've been one a survival horror trip recently, which resulted in me playing Outlast and Amnesia: A Machine for Pigs. Outlast was definitely a lot scarier and had tons of more gore, but all in all, I preferred A Machine for Pigs, and found it more unsettling when thinking about it after the fact. Still, I'd recommend both games to people that are fans of the genre.
Next step: working up the courage to play The Dark Descent.
Have you played SOMA? Looks really cool, haven't tried it myself though.
I have Amnesia: AMfP but haven't finished it yet, it gave me the creeps. Alien Isolation was tense enough for me, those games are on a whole another level. The whole atmosphere and the fact it plays below the sea makes SOMA interesting even for me though since I loved the Bioshock series.
SOMA sounds interesting, but I haven't played it yet. My next projects are Inside (made by PlayDead, the guys that made Limbo - so fucking excited for this one) and, once I decide I'm in the mood for more gorey horror, Outlast: Whistleblower. And after that, I'll probably have to play Christmas Shopping Simulator or something to come back down from all the horror - horror games are fun, but taxing.
After that... SOMA, maybe. And Dark Descent, if I ever feel like subjecting myself to that.
I would, however, definitely recommend finishing A Machine for Pigs. It gets a little fantastical towards the end, but the story is still really good and it has a lot more things to say than your average horror game. Plus, the whole atmosphere of that game is just so fucking perfect.