I believe it has more to do with the fact that they were fighting to preserve their 'Fatherland'. The German pilots were never rotated out of service they flew until the end of the war in death or otherwise.
[Wow, the only 'thumbs down'; must be an admirer.]
"A special Luftwaffe formation, the Condor Legion was sent to support General Franco's nationalist forces during the Spanish Civil War. This battle experience, fighting against the most modern Soviet fighters crewed by experienced pilots, allowed the Luftwaffe to develop a sound doctrine covering almost all aspects of air combat operations in the combined arms battle. Around 20,000 members of the Luftwaffe gained direct combat experience in Spain, giving the Luftwaffe a crucial advantage over its enemies during the first part of World War II.
"Until the development of allied long-range fighters the Luftwaffe remained relatively capable and kept the capability to inflict serious losses by the day fighters and night fighters.
"As modern as these aircraft were, they could not prevent Germany's total defeat in the air. In the end, the Luftwaffe lacked fuel, trained pilots, organisational unity and "safe" airfields.
"German superiority was especially felt during the first two years on the Eastern Front, given that the Luftwaffe enjoyed an advanced technical standard compared to the Russian A/F. Another factor was that it was employing highly trained and experienced pilots.
"From 1943 onwards however Luftwaffe superiority slipped away, as the Russian A/F recovered from its devastating initial losses, and Soviet factories provided planes to the frontline that could compete with their German counterparts. At the same time, the air battle over the Reich drained the resources of the Luftwaffe."
http://www.answers.com/topic/history-of-the-luftwaffe-during-world-war-ii
"Following the Battle of Britain, however, the Luftwaffe went into a steady, gradual decline that saw it both outclassed and outgunned by the sheer number of Allied aircraft being deployed against it. Towards the end of the war, the Luftwaffe was no longer a major factor, and despite fielding advanced aircraft like the Messerschmitt Me 262 and Me 163, was crippled by fuel shortages, insufficient production capacity, and a lack of trained pilots."
http://www.answers.com/topic/luftwaffe
It looks as though the Germans had a little more practice before the major combat of WWII thanks to the Spanish Civil War. They also had a distinct advantage in equipment at the start of the War due to their unannounced 'prior intention' of general warfare.
Both the Germans and Japanese suffered due to the losses of experienced pilots at the end of the War; Due in part to the fact that they never were able to be rotated off the battle front. Americans used experienced pilots as trainers, at least for a part of their tour of duty. J/S
8^{I)