Germany is definitely the most powerful civ of the bunch. The other civs can't really compare. For example, everyone is well aware of how great the barbarian conquering bonus is (not only do you get free units, but if you don't get the free unit, you get 75 gold instead, which 3x more than everyone else). Being able to field a ridiculously huge army (17 - 18 units easily) without spending a single hammer on military unit production is incredibly good.
Then their first unique unit is a half-priced pikeman. This means they get to have pikemen that cost the same to make as spearmen. And their pikemen are stronger than other pikemen. Ayup. I personally consider this to be the most powerful unique unit of the middle ages as pikemen lie on the same route as getting the knowledge tech for universities, a must have tech considering in this version of civ you can't trade tech and as such, you really need to be on top of your game in terms of research. All the other civ medieval units are on the combat line of research.
And their second unique unit is the panzer, which for some strange reason is cheaper than regular tanks and does more damage.
I think you'd have to be extremely unlucky to lose as Germany or be denied barbarians or something. Heck, in fact I think currently only Germany can defeat a diety level AI 1 on 1 because of the barbarian recruitment and pikemen spam.