I think civ2, because of the scenarios. After a while, playing the standard game can get a little dull, but when you can play any where, any when and edit the rules and graphics and unit abilities as you see fit, then it's like having 1000 games, not one. Sure, the graphics are better in civ3 and the AI is smater and more complex, but it lacks the element of user control and manipulation of the game environment which made civ2 so re-playable after years and years. Maybe when the civ3 editor comes out I will revisit this, but until then, civ2 is much more fun for longer.