I played both Civ IV and Alpha Centauri extensively - I've played every faction in AC to victory, and even played Sid Meier's Alien Crossfire, which is the putative update to AC.
Leaders in AC cared about your "government settings," much as current Civ V leaders strongly care about which ideology you adopt and whether or not you share religions. In fact, I consider Civ V AI to be superior in that certain Civs will weigh peace and war differently, and wonder chasing and CS-chasing differently. If you chase CSs, you WILL butt heads with Alexander and Ramkhangheng, since both those AI seek the alliance of CSs across the globe. Genghis? He don't care about that.
Exterminated a Civ? Both Attila and Ghandhi may consider you a warmonger, but Hiawatha may be willing to overlook all that if the enemy you exterminated was his mortal enemy (meaning he was at war with the Civ at the time). In addition, Attila probably won't mind that a lot, but Ghandhi will. In addition, Attila may not mind much, but he'll still happily declare on you just because he likes war. Ghandhi may hate your guts all game long, but he may not resort to war to punish you (instead, he'll aim at embargo and luxury bans).
That's a whole heckuvalot better than AC! Lots, lots better. Orders of magnitude better.