Ok, I finally got tired of Galactic Civilisation 2.
Maybe I'll reinstall Alpha Centauri.
This is the unofficial sequel to Civilisation 2, by his new company Fraxis. The planet is overgrown with a red alien fungus which hides hostile mindworms. You can choose to clear them away or unlock their secrets. I also like how every political, economical or social choice you make will definitely make someone unhappy. It was a perfectly balanced game in my opinion. If only Sid would come out with Alpha Centauri 2...