I disagree...I don't mean to play down the importance of the Air Force. In today's world any nation without a potent air force to defend its skies would be at the mercy of its enemy with a capable air force.
However the reason why Germany lost in WWII had a lot of factors and losing air superiority was way down on the list. Among the reasons that played the biggest role are
1) Tactical/strategical blunder of starting a second front with USSR(underestimating it and expecting a quick victory)...which effectively meant splitting of forces, materials, creating another supply chain, etc.
2) The sheer number of countries(with their own economies, industrial might, number of troops/tanks/etc.) that Germany was facing. Though Germany was marvelously at the forefront of about everything latest and greatest...it's just way too hard to fight so many different countries alone and come out on top.
3) Due to the second reason above...the attrition rate was just too much for Germany in terms of troops and equipment. Germany's population and industrial output couldn't replace the soldiers and equipment at the rate at which it was losing it.
4) Hitler's insistence on quality vs quantity...Germany went through so many iterative upgrades of its tanks, missiles, aircrafts instead of mass producing a tried and true design. This condition of being in somewhat of an eternal R&D really proved disadvantageous in comparison to USSR's approach of overwhelming Germany with sheer numbers. German tanks were much superior to Russian tanks but Russia made them in such a quantity that they could afford to lose more tanks and still have an advantage. Russians employed simpler techniques to deal with issues like for example the pins in the tracks of Russian tanks were prone to get loose and pop out...they simply had their troops carry hammers so they would hammer the pins back in every now and then. This kind of simpler approach was also used by Beatrice Shilling who employed an RAE restrictor to solve the engine stall problem for RAF fighters(during negative G maneuvers)...so that they could continue to use their current fighters with just a minor upgrade that could be achieved quickly.
For point 1...if Germany hadn't started a second front, it wouldn't have suffered all the casualties it suffered on the eastern front. It wouldn't have had its resources and troop strength bogged down on the eastern front and could concentrate all its might on the western front. Since France fell quickly, Germany could've focused more on its Navy/Air Force to gain supremacy on British Air Force and Navy...which would've enabled it to mount an amphibious attack on Britain and end the stalemate there before US even had a chance to enter with full force. Even if Germany would've still lost in this scenario, it would've taken much longer for the Allies to defeat Germany.
Point 2, 3, and 4 all tie together. The superior quality of German equipment just could not match the quantity of combined allied equipment(tanks, aircrafts, etc). Germany also hampered itself by not going for mass quantity(relatively speaking when compared to Russian approach) and instead kept trying to one up the enemies with quality. This further made it impossible to keep up with the attrition Germany was facing.