In addition to the many amazing games already mentioned, I'll throw in the 1995 gem "Ascendancy" from The Logic Factory. The user interface is a bit rough by modern standards but, for its time, it was a fascinating 4X turn-based strategy game (despite the broken "AI") with an impressive array of alien races with unique art and music for each. It's been in-and-out of the "abandonware" classification over the years, so there may not currently be any legitimate way to acquire a copy of the game--which is a real shame for those who might want to experience a nearly 30-year-old game that I think was groundbreaking for its time.
This is my first day on beehaw, and I'm planning to shift as much of what I previously did on reddit to this platform or others. Hopefully that will allow me to abandon reddit completely. I'm looking forward to learning more about this place and seeing how it develops.