The map is the most important part of any strategy game, especially a 4X game. I spent 18 months creating the map generation system for AtG, and although in retrospect it was probably a bit much it really is a cool system, and something I'm proud to show off and expect to continue using in future games.
My primary goal with the map generator was to produce realistic-feeling worlds. They aren't perfect, and I've fudged things here and there for the sake of good gameplay, but the goal from day 1 was something that felt right. There should be long mountain chains, vast deserts, lush regions, rivers winding down from high points helping quench the thirst of dense forests.