Oh, man. Alpha Centauri was more then just a strategy game, it was an adventure! Mankind surviving on an alien world that gets increasingly bizarre the more secrets your scientists uncover.
And the factions are divided by ideology, not nationality or race! That was an incredibly cool concept if you ask me.
You got the theocrats, science guys, eco warriors(?), militaristic dudes, capitalists, space North Korea, and the United Nations. And very scary aliens.
The best thing about these factions is that the game presents them in a neutral light; you have to make up your own mind about them. And your opinion will change with every game you play.
For instance, the Lord's Believers: insane fanatics of Christianity, or the last bastion of humanity in a sea of transhumans? Is the University of Planet a faction run by mad scientists, or by people who realise that knowledge is the key to survival for the human race? Are Gaia's Stepdaughters just filthy hippies that dance naked, or is their empathy with Planet the only thing that stands between them and oblivion? Are the mindworms and other alien lifeforms on Planet out to kill humanity? (Yes.)