They initially did had qualitative edge, couple with it ppl like Rommel, they were pretty good in tactics as well, they Indeed revolutionized the warfare e.g. Invasion of France & the 'blitzkrieg' on Poland
What i feel is that Germans became over confident, moreover they did some extremely stupid mistakes on Eastern Front, they didnt cared about gaining any local support, initally some Russians welcomed them as ppl who will liberate them for 'Bolshevism', but instead of using this local support they completely lost it, when these areas where handed over to Gestapo
moreover it was the obsession of Hitler (plus some stupid moves & over confidence) with Stalingrad which lead to total destruction of 6th Army(the Army about which he said, "I can March to Heaven with 6th Army), had he assembled all his units for one final Push towards Moscow, there was no way Russians could have stood the onslaught, In end there over confidence lead to slow progress in research for new weapons, e.g. i read some where that idea of jet A/Cs was initially proposed in 1941, but there was seen no need to fund the R&D here, they became really ignorant & many other reasons, but one thing is for sure no matter what was outcome of war Germans killed more Russians & Allied Forces & Waffen SS was indeed ppl were really Gladiators, in one of the Buildings in Berlin SS doomed Russikies in the end Russians brought down that building to get Rid of SS soldiers inside, one more thing i must mention was
COMPLETE FAILURE OF NAZI INTELLIGENCE, they were just terrible in this field ...
back to Japanese, I m thinking what If Japanese were not over Confident in Battle of Midway
their performance in Navy was terrible compared to USN, Japanese won each & every war in their history except ONE......
Anyways its all history, these nations have all potential to rise & shine.....