Medieval Total War is the greatest PC game I have played to date. It flawlessly mixes a turn based campaign with real time field combat. Each of the countries are specilized with location, religion, buildings, and units. It has the one of the most in depth stratagy components I have used both on and off the battle field. The Campaign mode is fairly easy to use once you understand it. The same is true of the battles. The battle totorials though are a must to go through or you will never understand how to cotrole the troops.
The only major problem is that diplomacy is almost useless. Your allies almost never help you, and there is no penelty for breaking alliences. Also the grafics are not as good as one might expect, but I perfer it that way because it is not nessicary to get a gaming computer to play a great game.