In his book, Saburo Sakai made some interesting observations.
He said the American pilots when the war started were extremely good as were the Japanese pilots. The American planes were much inferior which gave the Japs an advantage.
As the war went on the American planes equaled then exceeded the Japanese ones. By 1944 most of the pre-war Japanese veterans were dead and their replacements inferior.
He said the American pilots also declined but their far superior planes made the difference.
The Japanese had a small number of extremely good pilots. They flew aircraft that were world beaters in the hands of an expert, and which would kill a novice. The A6M is not spectacular in any particular. It is slower than the Bf 109, the Spitfire can match it for maneuverability. Almost anything with US insignia was better armed and more durable. What made the Zero a legend was the men who flew it. Once they died the very nature of the aircraft and its successors meant that there was no way to quickly bring up replacements.
In contrast the Americans brought out planes like the F6F and F4U that could beat the Japanese in every category, and yet were durable enough to allow novice pilots to survive their first missions and become experienced. The average pilot in the late war US Navy and USAAC were vastly better then the men who went to war in 1941. One reason for that was the US tactic of bringing home top aces to teach recruits how to better fight their aircraft. In contrast in Japan and Germany the rule was fly till you die. It did mean that the Axis powers produce super aces like Erich Hartmann, Günther Ral and Saburo Sakai. However it also meant that those super aces were supported by a bunch of guys who didn't know how to set their trim tabs correctly. Quite literally as late in the war Robin Olds shot down one German who was crabbing sideways in his Bf 109 because of failing to reset his trim tabs after takeoff.
I’ve read one interesting observation about US pilots, from both Japanese and German aces. Starting as early as the Flying Tigers, they were often amazed to see a single US plane, or just a few, turn into vastly superior numbers of enemy planes and fight against bad odds. They said the US pilots were fearless.