Book of Hours. It’s a strange game, set in the Secret Histories, the same setting that Cultist Simulator had. Unlike Cultist Simulator, which was rather gruesome, Book of Hours is a relaxed game, about cleaning out and restoring an abandoned library, reading the occult books left in it, and drinking tea with your guests.
Potionomics. While it’s primarily a puzzle game about brewing potions, it has a lot of heartwarming dialogue.
Settlers 2 (the original DOS game, not the remake). The Settlers series was what brought up the term “Wuselfaktor” (No clue how to translate this. There is an English explanation of the term in this article.), and imho Settlers 2 is (by far) the best part of that series.
Kerbal Space Program. I can’t say why this game makes me happy, but it does. There’s something strangely relaxing about drifting through space in free-fall, seeing the planetary surface pass by at high speed below.