Stelios a few more game recommendations for learning Mandarin:
Animal Crossing exposed me to a lot of vocabulary every elementary schooler knows but which I probably wouldn’t have learned otherwise. New Horizons has an excellent Chinese localization, or you can try the iQue version of the original Animal Crossing, which was the final update of the game, has lots of original content, and recently got a patch so that you can run it on an N64 emulator. There’s also a fan translation of Wild World, which is how I first played Animal Crossing in Chinese, but it had a bunch of problems. You couldn’t actually input any Chinese, so stuff like sending letters was semi-broken. I think now that there are better options, I’d go with those instead of the old WW fan translation.
A lot of Japanese dating sims and visual novels get translated to Chinese before getting translated to English. Most notably for this forum, the Windows version of Tokimeki Memorial has a Chinese translation.
Many console games without official Chinese releases have fan translations, or even dumps of old bootlegs. Just to give a sample of text-heavy games I’ve been thinking about playing in Chinese, there’s Persona 3, the Playstation version of Dragon Quest Monsters, Freshly-Picked Tingle’s Rosy Rupeeland, and Tactics Ogre. Obviously all the classics like the Final Fantasies and Legend of Zeldas have translations too. Some fan translations are simplified or traditional only, but idealy you should learn to read both anyways, since it’s very little additional effort.
In terms of Chinese-language originals, the two recentish indie games that everyone on these forums seem to like are FIST and Eastward. I haven’t played either, but you might want to give them a try. For big 3D stuff, I know The Legend of Sword and Fairy is a long running Taiwanese series that lots of people seem to like, and the newer games are on Steam.
You can also find a list of Chinese/Taiwanese games on Steam here.
Obviously there’s also Genshin Impact and Honkai Impact, which would probably be useful to play if you want to understand Chinese online-culture, since people reference them in memes all the time and they’re probably the most popular inspiration for fanart. I’ve never actually played them, and probably never will, but there’s a good chance you already have.
Hopefully that gives you at least a few things you hadn’t already thought of!