I knew an old air force LTC who was a P-51 pilot in WWII. He was so good a flying and at teaching that he was kept stateside the whole war - I'd rank his skill set up there with Hoover and Yeager and anyone else I ever saw on the airshow circuit; who's to say who that mythical best pilot is?Now that I have gotten older and studied WW2 aviation more, I tend to agree with you here. Best is very subjective. There are so many variables.
OTOH, I can think of someone who might have been a great ace or might have been killed; this way I got to know him and his children.