Quarantine owns, I still have it on the 3DO. But you reminded me that there’s a (sort of better IMO) PC only sequel to it no one knows about because it’s unfortunately titled ROAD WARRIOR: Quarantine II. It’s more of a linear game but it’s technically better and has a lot more mission variety. I also appreciate that it takes place immediately after the first game ends.
Anyway I mention the 3DO version because it’s real good and you’ll probably have better luck running the 3DO version in an emulator than getting the PC version working on current stuff.
My favorite games that can no longer be played that I did actually play are both DOOM RPG games and Aliens Online.
Aliens Online(1998) was awesome. I liked it mostly because of the way its interface helped with the tone and tactics you’d use in the game. If you were playing on the marine side you got to chat with each other marine players prior to a game starting and have access to a map of the level ahead of time. If you were on the alien side you couldn’t directly chat with each other but could access the “back end” of the map and see all of the air vents/etc. and could keep track of where other aliens were very easily while playing.
My favorite lost game ever though is Terminator: Future Shock. That game is amazing, I have gotten my original disk working on some newer-ish machinery sometimes but it’s very random. It’s one of the very few internally made Bethesda games that’s Actually Good and despite it being from the mid 90s (and actually pre-dating Quake for having a real time 3D FPS engine!!!) the way the game lets its level design tell the story and the atmosphere and openness of the levels is just nuts, and you can see the sort of early DNA of what they would attempt to do with Fallout 3’s scenery. Plus for an FPS at that time, I mean you get like 12 different guns and five different types of grenade/explosive things and all of them are useful. There was a really good sequel also that’s also never going to officially get released ever again.
When I say the DNA of Fallout 3 is in there, I should have said the DNA of Bethesda games. Bethesda had made a couple of Terminator games previously, but you know how Daggerfall works, and how even Skyrim works and the way there’s a hard divide between “interior” and “exterior” and a lot of those other engine quirks, that’s all there in Future Shock and that’s amazing.