I'm probably cheating putting the expansion pack at #1, but The Conquerors turned Age of Empires 2, already one of the better games of its kind, into what may be one of the best Strategy games ever made. The added scenarios and factions alone make this a great game, but what helps this get to the top of a list of Historical Games is how a wide number of medieval cultures were represented as well as they were.

For example, like in real life, the playable Aztecs lack cavalry and gunpowder-based units. However, their Infantry and Monks are top-class, symbolic of the importance of religious wars for that civilization. Likewise, the Huns are given a realistic emphasis on cavalry raids, featuring mounted units with bonus damage against buildings, and their nomadic nature is shown through their lack of population caps from housing.

A great expansion to an awesome game, this game added awesome campaigns and units.