My list and reasons (no particular order)
Remember this isn't a greatest athletes list, it is a greatest CHAMPIONS list. All to do with winning, not athleticism, although I'm sure that many on the list would be on that other one too if I made it.
Here goes...
1. Joe Montana, Football- Amazing cool under pressure, was the architect for four super bowl rings, and was always there when it counted.
2. Michael Jordan, Basketball-uh, duh...
3. Alexander Kerelin, Wrestling- 3 time olympic gold medalist, 1 time silver, did not lose for 18 years, was a monster, would have never lost if he didn't go down on a technicality.
4. Kelly Slater,Surfing- 9 time world champ, first title at 21, most recent at 36, and is still the best in the world at 37 and is in the hunt for his 10th title. Incredible athlete, has pushed the sport far outside of its own realm. There was surfing before Slater, and there is surfing now.
5. Bekele, Distance Running- The God of distance running, has the mentality that tells him only he wins, and the legs to take him there, and that he does.
6. Tiger, Golf- revolutionized everything, is basically unbeatable for the world title, and is a freak of golfing nature.
7. Phelps, Swimming- well, ..obviously after taking down Spitz's records, nobody will argue with this one
8. Bolt, Sprinting- After this Worlds this is now safe to say, in just two years, from an also ran, to the all time greats of everything.
9. Lance Armstrong, Cycling-Won the tour a mind boggling 7 times in a row, and came back from a three year break, and almost took it all again...amazing
10. Al Oerter, Discus- won the discus in four straight olympics, and in two was so hurt that he could hardly breath. He was as if Hooker came back three more times in the olympics over a 16 year period and won with the same injury he had this year twice.
Honorable Mentions
Edwin Moses, Hurdler- never lost a race
Sparticus, Gladiator- killed everyone in every arena before thousands including the coliseum. Was so good at combat that he led a slave revolt that seriously shook the roman empire. Would've liked to have seen this guy in action, probably was good stuff.
