1) Michael Phelps
2) Lance Armstrong
3) Ali
4) Pele
5) Jordan
6) Babe Ruth
7) Ronaldo (Brazilian not Cristiano) - I only say this because if I say Ronaldo to my parents they know the Brazilian, but not Cristiano. Although these are only two people, I am pretty sure most parents would at least recognize his name.
8) Lin Dan - While this name means nothing to people outside of Asia, its hard to overlook that chunk of the world with their Billions of people...
I made my list based on "Most Recognizable." Just their names, not their faces.