To be "great" an athlete has to achieve success at the highest level.
Pele definitely deserves the accolade. I dislike Maradonna, never forgiven him for his cheating in '86 and his repeated drug abuse.
I wouldn't nominate players from days of 'yore' the game has moved on, its much faster and more skillful now. I hope Messi and Rooney achieve greatness this world cup