Me, I prefer Civ III because of its complexity. Plus the fact that you *must* make war to get the raw materials you need (iron, rubber, oil). :Titan:
Civ 2 was fun, but the spy unit was a bit too strong: I never built any big nukes, I just loaded up transports full of spies. I shipped my spies to enemy coastal cities, infiltrate and plant nuclear device! Repeat that 4 or 5 times (every time the AI reacts by moving more units back into the empty city).
It was about the only way to fight a Fundamentalist power. They have too many units, so waging nuclear war through spies worked okay. Just don't ask about the pollution...