2 words... can't. stop.
Civilization IV should be recognized as a weapon of mass destruction instead of a video game. This game is so immersive that you will think that you are Ghenghis Kahn, Napoleon, or one of the many leaders in the game. It's just tough to stop. You just "have" to wait until that Wonder is built that might give you the edge... You just "have" to wait until you research that technology that will give you the edge in the war against the French... The multiplayer is now revamped giving you some much better options and smoother play. Civ IV (and all the civ games for that matter) is probably the most replayable game ever created, and it is so incredibly moddable thanks to the Python script. You can go to any Civ site such as Civfanatics.com and download mods, custom scenarios, maps, etc. or just mod it yourself. I would highly recommend this game to any turn-based strategy fan.