I have to confess that I lost a lot of my life to the original Civilization game, back in the day (err, around 1991, IIRC). This was the only game that I've ever played literally until the pink glow of dawn came in through the window.
None of the later ones caught me as much, but my life was pretty different - it's hard to stay up all night playing computer games when you have small children.
But #2 Son has heard me talk about it, and sends me this review of the new Civilization V. It looks pretty cool.
Of course, there's also the Open Source FreeCiv, which is pretty cool, too. Not as much new eye candy, but you can play on-line, and did I mention the free part?