Patient Gamers

For some shorter experiences I haven't seen mentioned when skimming through a few comments here, I definitely recommend trying Transistor. It was one of the strongest emotional experience I've ever had in a game. I've managed to play it in a single sitting, but it is around 6 hours long. Supergiant games make such a uniquely perfect audiovisual experiences, that every game from them is a treat, but Transistor is the strongest emotional experience I've played from them.

Another one would be two-hours long walking simulator with amazing environmental storytelling - What Remains of Edit Finch. You can play it in a single sitting, and it's gorgeous and really well done.

You should also play Hellblade: Senua's Sacrifice . It's also around 8 hours long, and you definitely want to play it with headphones, it's such a strong emotional experience. The audio and game design is so well done, and the game has stuck with me for such a long time. It's one of the few games where just seeing the trailer again tears me up and gives me chills. And after you play it, I recommend watching the documentary about how they tried to protray the mental illness of the main character through game design - it's such masterfully done that I didn't even realize most of what they are doing, but it has stuck with me and it worked wonders to make the experience even better.

And for some even more unique game design - Before Your Eyes. What makes this experience so strong is the whole premise of looking over your life and memories after you've died, with the main mechanic of how to advance time being by blinking - physically blinking, because the game can work with your camera. That makes for a pretty strong metaphor that makes it even more emotional experience.

And just to mention some games others have mentioned, to add to their recommendations - Outer Wilds, Ori and the Blind Forest, Life is Strange, Planet of Lana, all are really good games!