Depends on how you're trying to play. Are you playing for a high score? - it takes forever, though not so long I guess with Civ1. Are you playing OCC? - I can win a Civ1 OCC game in just two hours. Or just playing a normal game to win? - depends on the style: if you're playing isolationist on say Civ2 you can have a quick fast game, often without any combat. You rarely get the change for zero combat on Civ1. The more combat the longer the game. The higher the desired score the longer the game.