Roommate Jim introduced me to Civilization back in the stone age of PCs in 1991 (it was a DOS game). A few years later in 1996 I upgraded to Civilization II, and lost countless hours playing that version - and I mean lots and lots of hours. It is generally regarded as the best PC strategy game of all time, and I agree with that assessment.
Civ II was around for half a decade before Civilization III was released in 2001. I tried it out and didn't like it. While the graphics were vastly improved, I felt the game play wasn't as good and had a lot of problems. So I went back to Civilization II with the better game play and crummy graphics.
This Christmas they are going to try again with Civilization IV, whose game designer recently had an interview with Gamespot. I'll go ahead and put it on the Christmas list, hoping that along with the pretty graphics that they'll actually improve game play this time around.