I still haven't played a better 4X strategy game.

One of the best aspects was that it provided so many different ways to play that were effective. Usually in Civ-games, no matter how they try to design around it, there's no real alternative between just rushing technology and pumping cities to snowball.

One of my favorite things to do was to use the terraforming abilities as weapons, and build mountains or flood the low-lying land. Or you could encourage the native life to go wild and take out the other players.

The unit designer was also fun; it's one of the few in games where I have actually bothered to build out specialized units for different roles - usually it's either pointless or too complicated to bother with.