This is in no way supposed to be taken seriously.
If I read this thread correctly, it seems that the Persians had a very balanced army composition. Not only that, compared to their Greek counterparts, the average Persian received far more training and exercises than the average Furthermore, there seems to be a significant number of professional full time Persian soldiers who train professionally compared to Greek city states that drew up militia from citizens when it needed to and put them through a break-neck boot camp program before sending them off to fight. So taking all this in, there is a question that is bugging me by the evident military superiority of the Persians:
Why didn't they conquer Greece?
As has been said, the Persians had a standing army. From this I think they would have had military academies too to keep their military traditions, strategy, and tactics up to date. They actually had cavalry worth a damn compared to the Greeks, and probably used them properly too. In fact, given the cohesiveness of the Persian state, they could probably have drawn up more full time or at least notable strong men to field in their armies than the Greek states could field altogether, and this isn't including the levies that could be drawn up. So in the face of this, how could Persia fail at taking over Greece? Their martial ability must have been superior to the Greeks individually and cohesively as an army. Are the Persians just spectacularly incompetent? Given this view, I think they are. Sure you can argue that there are balancing issues in the game between Greek and Persian forces, but it seems to be the case that Persians, despite their multitudes of military superiority just can't bring it together to beat an army that was drawn from the streets of Greek cities.
The Persians are like the enemies that fight the Imperial guard in Warhammer 40k you know? Bio engineered, superhuman monsters, blessed by Eldritch Gods, in possession of several thousand years of battle field experience; biological monstrosities from beyond the stars, and technologically advanced metal space zombies, space elves, and space orks can't beat a bunch of normal ladies and gentlemen wearing compressed paper armor and wielding the galactic equivalent of a flashlight. To put it into better perspective, said monstrous forces had ten thousand years to put down these bunch of people. Like the Persians, this question applies to them equally in that they've failed to accomplish what should have been a trivial goal given a generous amount of time:
What's their excuse?