perhaps the reason for that isn't a level of intelligence -- to this day i still can't solve a maths question faster than my calculator

civ3's hardest difficulty-Ai is probably just following a specific strategy based on certain factors including the player's decisions, and doesn't deviate from that strategy.
if my youngest brother or my dad knew how to program, and could create their own Ai in "Age of Empires 2: Conquerors", they would very easily be able to make an Ai that no human could beat.

julz