writehooks, you make great points.
Taking a worldwide perspective, you have to include sports that the world, and not just the US, cares about. And being famous around the world is also important.
I would like to add another popular world sport that has not been mentioned: cricket. Cricket is the ultimate gentleman game, and there are more cricket fans in the world than baseball fans. Cricket is especially popular in the UK where this poll is being held. If the greatest baseball player of all time, Babe Ruth, is included then the greatest cricketer of all time, Sir Donald Bradman, should also be on the list.
As far as sports legends go, worldwide, I would list the following 10 in no particular order (You have to have two football players in a worldwide list because of its popularity in the world):
Carl Lewis (huge impact overseas and arguably the greatest track and field athlete ever)
Sir Donald Bradman
Edson Arantes de Nascimento (ie Pele)
Michael Schumacher (although I'm not familiar with the sport or his impact)