This simulates a tile-based planet map. Animals grow and evolve, and things like atmospheric concentration and other aspects like surface albedo can be altered. More a toy than a game. Had a lot of fun playing with the levers.
1990 release – it’s still playable, though it’d feel pretty ancient and will not be very beautiful.
I haven’t played SimLife or Spore, and there might be some similarities there.
I’m not aware of anything else that’d be comparable.
EDIT: Liquid War. This is open-source and part of the GNU project. One has a map with some areas closed off and some open space that liquid can flow through. There are two or more “blobs” of liquid of different color; each is attempting to destroy the other. Your blob is attracted to your mouse cursor. “Moving into” a pixel of the other color eventually converts it to your own. If two liquids meet in a bottleneck, they tend to stalemate. One wins by getting liquid on multiple sides of the opponent’s liquid, so that one can move one’s own liquid from multiple directions into it. Maybe a bit closer to a tech demo than a full-on game. I wouldn’t call it mind-blowing, but it is free and as far as I know unique, and I had fun with it.