I agree with Izlude. A very fun game to play. Lone and I play this in multiplayer and singleplayer. Its fun and more than worth the buy. If you can I'd say buy the previous versions of Civ also. They were just as great as Civ 4 in their own ways. The only Civ games I don't have are the original and the expansions for Civ 3. Civ 4 is so much fun. I usually played as America but now I play as Germany because that's the Civ I used online with Lone and I just got used to them. Plus overall I generall get luckier with them in the beginning game placement. We usually just play a regular game with 10 comps because if its more in the later era my computer crashes. We ally up against whatever comp decides to stick his nose in our business.
In our current game France (Napolean go figure

) is trying to destroy me, at first I was worried because of the size of their army, but its turned out to be alright. They just keep throwing cannon fodder at me as my pikemen get experienced. I did have a macemen unit, but they managed to kill him after he took out 2 swordsmen, 2 axemen, and a warrior group. Poor guy defended Hamburg well.
As you can probably guess, I'm a HUGE fan of the Civilization series.