I literally just posted about a few of these in another thread. :)
Decent: Freespace and Freespace 2 are the best Space Fighter - Dog-Fighting Tactics games I’ve played. They still hold up to this day. And the voice-acting is great.
Dungeon Keeper and Dungeon Keeper 2 are also solid games, although more in the silly corner. Dig out a dungeon, build rooms to attracts creatures of the dark, train them and go to war against the foul knights and kings of the overworld.
The OG Fallout games are always worth a mention. Fallout and Fallout 2.
If you’re into old disturbing point and click puzzle games Sanitarium is a classic.
Or a bit more laid-back storytelling with mysteries, maybe? Then Oxenfree is worth looking into.
In the FPS category I recommend the Metro games. Well, the two first ones anyway. Metro 2033 and Metro: Last Light. Stealth is optional, but advised. :p
I’d also be amiss not to mention Soma. It’s a scary game and a solid mindfuck at the same time. Approach with caution.
That’s my list for now. I hope there’s something in there you can use. :)