Speaking of Earth series, I'm pretty sure a little-known game called Warzone 2100 is in the same series. It seems to be a somewhat more primitive version of the same game engine, and I'm fairly sure it's the prequel to Earth 2150.
EDIT: I LOVED Exile. I spent two years trying to figure it out before I realized you NEEDED the hint booklet or guess the random letter/number combinations to some of the passwords within the next ten years. Silly me, I was trying sensible things.
For example, the first quest of Exile 2, slaying the Nephilim chieftain. I wouldn't be able to get the password to go in the back way, so I'd storm the front and die in 10 seconds lol.