It is a turn based game, and it can end early if you are conquered. However if you make it to 2050 in quick mode, assuming you have a modern computer, a game o

It is a turn based game, and it can end early if you are conquered. However if you make it to 2050 in quick mode, assuming you have a modern computer, a game on Earth2 / Huge may take you 2 to 3 hours if you are familiar with the game and you do not get into many conflicts. However this is not the way Civ is meant to be played. You are supposed to inspect your cities, make sure citizens are healthy and happy, emphasize culture, science, population growth, economy depending on what is best, build a balanced army, conduct diplomacy, spread your state religions and corporations, keep an eye on your allies and adversaries, spy on adversaries and sabotage their stuff, etc. The game pushes you to take sides and if you don't you will piss off everybody.