Civilization 4 is one of the greatest games of its type ever made. It may be better than any Age of Empires game. But there's a reason it is not #1 here.

Its problem is that for a game based on the course of history, the game sometimes does a poor job at representing this. Civilizations have a couple of unique traits, such as Rome having a stronger Legion for the same price as a generic swordsman, but it is not enough to fully set them all apart. Even considering the millennia covered, it is a bit disappointing. Fortunately, the addition of Leaders in this iteration, with personalities and priorities that influence game mechanics, mean that much of the flavor is still intact.