The Germans certainly were well versed in both aviation as well as design and technology. The Japanese were too. Neither could be taken lightly. In the European front, the edge the Germans had was they didn't have to worry about range, as we were the ones flying the long distance to their backyard. Same kind of issue we'd see in Vietnam in regards to Hanoi/Haiphong, though I don't give the North Vietnamese pilots the same level of credit I would give German and Japanese pilots, as it wasn't so much that the NVNs were good, as it was that the USAF had failed to train and dropped the basics of dogfighting for all-missile technology.
But going back to WWII, some of the German designs were indeed interesting. Take, for instance, the BF-110 heavy fighter/interceptor. As a bomber killer of heavy bombers, the sheer destructive power of 2 x 20mm cannons and 2 x 30mm cannons is amazing, even moreso the B-17 I cite at 1:28 that is just taking the brunt of the Bf-110 attack and keeping on trucking. Absolutely amazing. Can't imagine having to have flown heavy bombers back then through that. If Id been flying back then, Id picture myself to have been a A-26 Invader or A-20 Havoc guy, or an A-36 Apache guy.