I believe the immense kills achieved by Luftwaffe pilots was more to do with operational procedures and tactical considerations than aircraft superiority (note the 109 in my sig, if anything I'm biased TOWARDS to Messerschmitt).
German pilots basically lived at the front and could be fighting every day, but Allied pilots rotated. German aces continued to fly in combat, whereas Allied aces were promoted up the ranks or sent to training camps to share their knowledge with the next batch of nuggets.
Also, the German doctrine, centered around the 'finger four', dictated the leader (which would be the most experienced pilot, so Hartmann, Rall, Nowotny etc.) stalked the kill while the wingman covered him, so these pilots accrued many kills.
Futhermore, many of these aces flew on the eastern front during Operation Barbarossa, where they scored many victories against inexperienced Soviet pilots in often obsolete machinery. (Except of course Marseille, who scored almost all of his against Western Allied aircraft ^_^)
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