The Germans had been perparing for war for years. Their technological development was geared to make more and better weapons, their production was geared toward producing war materials, they had been stock piling fuel and supplies in preparation for war. They had been developing war experience, starting in the Spanish Civil War,in officers and troops.

The Allies were doing everything to avoid even the thought of war. Only in naval technology was the British investing in development. The only development the French spent anything on was the defensive emplacements on the border, which was fighting WWI again, a failed strategy.

The French were deeply divided, between the right and the left (sound familiar?) and distrusted each other more then they did the Germans. Crippled their ability to perpare for war and respond to the attacks that came.

The German generals look good, but a lot of that is due to the above, and due to the absolute political hacks that the Allies had in place before the war. The French were particularly fascinating, politics put the worst in place (again, sound familiar?)and they paid for it.

And the early gains that the Germans made gave them some of the most defendable borders that any general could hope for, except on the eastern front.

The Allies also were fighting the Japanese and their forces were split.

American soldiers, once they gained the experience that the Germans already had, and got improved weaponry to match the Germans, were better, more flexible and more dedicated and more capable. Only elite German units who got the best of everything could match them.

By the end of the war, the Allies had better equipment in every area, except missile technology.

The German as a supersoldier is a myth, pure and simple.