Except for one big difference...
those German designs were vaporware. The Germans had brilliant engineers who kept designing futuristic planes right up to the minute Nazi German collapsed. They were brilliant engineers who were totally oblivous to the world around them. For the most part, they were defeated by masses of weapons that were far less sophisticated than the German weapons (with the possible exception of the T-34 tank) but were able to be produced in staggering quantities. As Stalin once said, "Quantity has a quality all its own."