It seems to me that people need to define their terms. In my mind, the greatest player of all time can't be determined in this world. In heaven, the angels inclined to bet on such things could take all of the players in question, give them perfect health, give them their choice of equipment of varying styles, time to practice, and then have them play against each other for a billion tournaments on a million different courses. The player who accumulated the most wins, assuming the difference was statistically significant, would be the greatest player of all time.
Unless there is an afterlife, this will always be a thought experiment. We can use data to improve on it, but we can never know for sure.