Hellcat has highest kill number and win/loss ratio (18:1)- I don’t have current Hurricane numbers, but if I remember correctly they were less than half of this- Here's some info:
This is one of those debates that can never be resolved because of the variation mentioned before and because pilot experience was far more important than the platform (top German aces stuck with Me 109 long after it was surpassed by FW190).
However, on average, I would nominate the Corsair F4U. It was both fast, highly maneuverable, well armed and excelled in every role it was given. Sure the mustang was the best long range escort, the Zero or FW190, may have been most maneuverable, the ME262 was clearly fastest, but the Corsair could tangle with any of them in any environment and with pilot skill averaged out, they were in a position to win against any of them (short of a full speed strike from a ME262, but obviously this is apples and oranges).
The US intentionally spread the risk among many similar designs, so the differences are really narrow. But I honestly believed that if we could test all platforms in all major fighter roles, the Corsair would win by a nose.