X3 Terran Conflict. It might take you 30 hrs to figure out how to do literally anything. But man, you can go from piloting a frigate telling 3000 ships to attack a station, to deploying spy sattelites so you can route your space weed smuggling ships away from the law/pirates, to piloting an attack fighter in the thick of the battle you just started... all in a single breath... once you've learned all the keyboard shortcuts, that is.

Starsector?