Alpha Centauri does look interesting. And it's one of the goals in Civilization Revolution. You can win through Domination (capture all other civilizations' capital cities), Culture (create a total of 20 great persons, wonders, and converted cities in any combination, and build the UN), Economic (create the World Bank) or Technological (be the first to reach Alpha Centauri). It's good fun, but if you've already won domination with a civilization and you try for economy, just to be buggered by the blasted French the game can get frustrating. Fortunately, a strategically placed blockade should put any London attack at bay (Except for the backstabbing Spaniards).
Yuki, I wouldn't think you would want Custom Game options. Everything seems stacked evenly for me, and playing is good fun, despite the tense defensive battles that the Greeks put people through.