Based on the wording, I have to take a different approach.
I've never been one for jumpscares, for me metaphor, psychology, and loneliness are the best way to get my skin to crawl and have it feel legitimate:
Silent Hill
Siren: Blood Curse
Further, since it says "best scary" games, I will include high quality horror themed games:
Cat Lady -- STELLAR story writing, and extremely artistic.
(Silent Hill, again, likewise, same with Siren)
Last of Us -- This was kind of the game that got me searching for horror games, especially ones based on story.
I'll also include ones that I consider good in other respects:
Imscared -- a pixel horror game, it's very clever in multiple ways. It's not a deep story, it's got some jumpscares, but its... complexity is what wins it credit.
I've heard a lot about a game called White Day, but I've only ever seen it played on easy, which nixes most of the scary things about the game, apparently. As such, I can't give it a fair analysis, but it was worth checking out. It, similar to Siren has a REALLY beautiful otherworldly element at one point that is absolutely fantastic.
Afraid of Monsters and Cry of Fear -- The way they portray the enemies, spasming and really quick, is a really unique (especially for the age of Afraid of Monsters) way of portraying horror enemies.
I've yet to find a good playthrough of the Call of Cthulhu game, but I've heard it's pretty dang good, as well.