I simply fell in love with Daughter - Burn it Down from LiS: Before the Storm. It is so nicely depressive song - the lyrics and even the style she's singing it. And yeah, I think even the scene where it is used helped this song to become my favorite. Main theme and other songs from this game are nice as well.
But the most favorite gaming OST of mine of all time is Dragon Age Inquisition Main Theme. I spent a lot of time with this game.
I really liked Dragon Age Inquisition Main Theme as well! Sometimes I look for the metal and piano cover of it too. There's something about the music that evokes the feeling of the first time I played it years ago. But my favourite would be The Dread Wolf OST, it sounds sorrowful yet so majestic.
Goddammit, Solas!