The problem with most games is that they end, and become just a fond memory. The problem with most strategy games is that after a while playing them, they beome a routine, even monotonous.
Not so with civilization 4! This game is a world in it's own right. You get to control all of history, and live it your own way. There's almost nothing that you can't do.(involving many famous leaders, religions, science\technologies....)
The game is literally infinite in posibilities!
What I really like is that you can play the game according to your own personality and still win. If you want to be warlike you can be warlike. If you want to live the whole of history without a war, you can if you want. Unlike most strategy games, for once here you feel truly in control. You play by your moral rules.
It's also the most worthy game ever, being very educational and responsable when it comes to relating element of history.
And don't forget that this game is also loads of fun and pretty easy to get the hang of.(unlike most strategy games)
The only down side is this: How on earth is anyone ever going to make a better game! This truly is the pinacle of video gaming!
So, if you've got a brain and like games that make use of said organ, then buy this game and let you brain boogie!