Project Zomboid for me. It's kind of strange since the game can be super stressful at times, but once you get past the initial stage of the game and have a good base setup, you can spend a lot of time just surviving. Farming, reading books you've found, cooking things, it can be a very relaxing and meditative experience.
Outside of that, I guess a more typical response would be just about any JRPG, particularly the Final Fantasy series. Some of my most comforting memories are just me getting back from work, sitting back in my chair and slowly playing through Final Fantasy X or XII.