4X style games like Civ have gotten no love from AI developers. As others have pointed out Starcraft has been worked on by serious AI researchers.

I suspect 4x style games will be among the hardest computer games for AI to tackle for several reasons. Just off the top of my head.

1. * Data sets to train on are smaller because individual games take much longer
2. * More complex rules sets
3. * More things to manage
   • * City/planet development
   • * Unit design (some games)
   • * Combat
   • * Exploration vs Exploitation
   • * Fog of war
4. *Multiple victory conditions

Some of those things RTS AI's already have to deal with, but I think 4x game are more complex overall.

I'd kill for a great Age of Wonders III AI.