Gann never tried to land on a carrier. I am sorry but that is the most difficult area of operations . Its the major criteria in this case
Just because he didn't doesn't mean he couldn't therefore, IMHO, your statement is bollocks. Not decrying EB or any other Naval aviators, but somebody mentioned about being given the opportunity put a lot of the names mentioned in 'the frame' where other equally skillful hands were overlooked.
The question was the greatest pilot ever, not who has the most types or who has the most carrier landings or the largest number of hours.
As has been said, many 'unsung' - the 'few', bomber command, Doolittle raiders, Tuskagee... I could go on.
They're all 'great pilots' -way above my 'pay grade!'
DD