Dwarf Fortress, full stop.
1000+ years of virtual history, then you dive down and either wander the world as any number of heroes, or you can build a, um, dwarf fortress.
Different starting conditions can do anything from making a single island amidst a planet-spanning sea, home to hundreds of bloodthirsty monsters and one naked barbarian warrior, to a world dead of all life (I recall one person on the forums did this with an adventurer who just hunted every animal extinct and killed every civilized creature, which was a little easier since it was a small world), to an epic war story between a once continent-spanning dwarven empire and the goblins that advance every day to wipe them out.
One of my fondest memories was when I played an adventurer, learned the secrets of life and death from a necromantic tome, lost my hand in a fight, and then RE-ANIMATED MY OWN HAND to fight alongside me.
Okay.
I uploaded it on FileFactory and on mediafire. The file is, again, for Civ III: Play the World. Also, I have a Spanish version of Civ III (I live in South America) so this is a file used with the European version of the game. I'm not sure if it would work in the USA version of the game. Does it?
> I liked the idea that everyone had tons of technological know-how but were starved for the resources to actually put that know-how to use, and spent most of the resources they were able to scrape together into building the next salvo of nukes to immediately fire off at their enemies
I know this is a few weeks old, so I'm sorry, but you might be interested in the old Doctor Who storyline "Genesis of the Daleks". Basically, set on a planet where two races have been fighting each other for centuries; the planet itself is a radioactive wasteland where mutant abominations roam the wastes, the races live in shielded cities, both sides are trying to build the "ultimate weapon" to end the war, and the war has progressed on for so long that they basically use any technology they can get their hands on (one soldier is using a bow and arrow but has a geiger counter, trenches are propped up with corpses to make them appear fully manned, etc).
Maybe here:
http://www.myabandonware.com/game/civilization-ii-multiplayer-gold-edition-3jb
Edit: Hmmm, it seems like it's the OS9 version. That will not work on OSX. Use the Windows version and the "Instructions for getting it working on Mac OS X". Wine is the thing.