Civilization III is the greatest game I have ever played.
I classify this game as a turn based empire builder. There are many differences between Civilization and other empire builders though. For instance, Civilization is by far the most in-depth empire builder that I have ever played.
You start out in the stone ages with warriors and settlers and basic improvements. You have to expand quickly to stake your claim on the world, because your opponents will be doing the same thing. After the expansion phase is over, you can focus on isolation, or you can use your military might to take over other areas of the globe by waging war on other nations. All the while, you must manage your economics to have a perfect balance of luxuries and technology because your technology is a major determining factor in this game. Technologies can start and end wars in this game, keep up with them!
You eventually work your way all the way up to the modern/informational age, where you will have modern military units like marines, modern armor (tanks), planes, ships, etc. The variety of military units in this game makes it possible to fight strategically and even win a war if you are down. You just have to think about what you are doing.
The last subject I will touch on is your ability to build "Great Wonders". Starting out in the stone ages, there will be wonders available that will provide great benefits (along with a great cultural improvement) to the nation that builds them. For example, if you build the Pyramids, you will get a granary in every city (I know that must mean a lot to you.) and this is very useful.
Overall, this game is the best I have ever played. I have owned it for over a year now and I still play it constantly. It's pretty safe to say I am addicted to it. Buy this game!