Civilization is a mammoth game. Only played it once. Lasted something like 10 hours, including teaching.
Very true to the themes in the video game; I've never actually played the video game but watched a little. Everyone gets a leader with individual powers/benefits. Many routes to victory (culture, technology, war, etc), no obvious paths, room to change strategies at any time. Pretty awesome, just need a good group for such an investment.
I've been told it can be as short as 3 hours if everyone knows how to play (we had 3 new players).
Would definitely play again.