ok back to topic....
Sid Meier's Alpha Centauri and its expansion Alien Crossfire
hey no bitching about Gal Civs 2, that game is the best.
Alpha Centauri seriously is the best thing ever (I think the original is superior to the expansion, which IMO only adds unnecessary and confusing things and factions that are awful, buggy or poorly balanced).
GalCiv2 was indeed ruined for me by the devs' terrible sense of humor, and also because balance really isn't that great and the AI can be pants-on-head retarded sometimes. After playing GalCiv2, you understand why other games' AI is so stingy with tech trading; GalCiv2 lets you play the peacemonger neutral party, trading tech off everyone to become a superpower, then quietly build up a giant army in a corner of the map while everyone completely ignores you and never ever bands up to defeat the growing menace.
MOO3 is essentially Spreadsheets: The Game. Don't bother. Same with Aurora.
Colonization has limited fun value due to balance issues and weirdness, but it's a kick if you just want something to tool around with for a while since it's a corner of the genre where basically nobody ever goes.
If you've never played Master of Magic, you are seriously missing out. Grab DosBox and enjoy it today; it's a shining jewel.