Enjoyable, but not as intriguing as I had hoped.
The main reason as to why I even bought the game, sad to say, was from the television commercials that I saw. I should have paid more attention when I grabbed Civilization 4 off the shelf and realized it was a turn-base stratagy (TBS) game and not what I was expecting at all. Nevertheless, I bought the game and I actually found it that Civilization 4 wasn't as bad as I thought it was, once I realized it was a TBS.
As stated before, I had never played a Civilization game before; So, learning to play this one was fairly simple. Also, the fact that you can greatly vary the difficulty level makes playing much more enjoyable. There is nothing worse when trying to learn a complex game like Civilization 4, only to find out that the easy difficulty level is too hard for a first time person, leaving you feeling cheated and causing you to turn the game off - never to play it again.
If you grow tired of ever taking on the computer, and you have internet connection, jump online and take on some real people. You are given a variety of ways to play online: quick matches that can go as fast as 30 minutes to drawn out matches that can last up to 8-10 hours. You can even play via email; although I'm not entirely sure how well that method works.
The graphics are well enough to keep your attention and to not leave you thinking they are dated. Sound effects are good and the music is a bit on the dull side, but it does a good job of adding to the atmosphere.
You could build a single map and replay it over and over again, and the game would never end exactly the same. So the replay value of this game is very high, as long as you greatly enjoy turn based games.
When you play single player, be sure to learn how to get a helping hand from computer controlled characters. There is nothing worse then trying to take on two or three different nations as they gang up on you.
This is the only bit of advice I give to new players starting to learn Civilization 4. Learn how to make friends with people/computer players that you are going up against. You can please them all, but having at least 1 person to help you fight others is a great resource.