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1. Michael PHELPS

2. Usain BOLT

3.Cristiano RONALDO

4. Kazuyoshi MIURA

5. Diego MARADONA

6. Mohammed FARAH

7. ZICO

8. Zinedine ZIDANE

9. Saori YOSHIDA

10. Miroslav KLOSE

11. Johan CRUYFF

12. Kei NISHIKORI

13. Sergey BUBKA

14. ZE ROBERTO

15. Francesco TOTTI

1. Eddy Merckx
2. Pelé
3. Usain Bolt
4. Michael Phelps
5. Bjørn Dæhlie
6. Michael Jordan
7. Petter Northug
8. Carl Lewis
9. Johan Cruijff
10. Gunde Svan
10. Ingemar Stenmark
11. Dick Fosbury
12. Fausto Coppi
12. Björn Borg
13. Serhij Bubka
13. George Best
14. Eric Heiden
14. Wayne Gretzky
15. Lev Yashin
15. Vladislav Tret'jak

Why not?

1. RONALDO

2. Michael OWEN

3. Gianfranco ZOLA

4. PELÉ

5. Michael JORDAN

6. Alex MORGAN

7. Peter SCHMEICHEL

8. Michael SCHUMACHER

9. Valentino ROSSI

10. Federica PELLEGRINI

11. Saori YOSHIDA

12. Thor BJÖRNSSON

13. Haile GEBRSELASSIE

14. Midori ITŌ

15. Valentina VEZZALI

1. Ayrton SENNA
2. Michael JORDAN
3. Diego Armando MARADONA
4. Nadia COMANECI
5. Serena WILLIAMS
6. Lionel MESSI
7. Paavo NURMI
8. PELÉ
9. Michael SCHUMACHER
10. Eddy MERCKX
11. CRISTIANO RONALDO
12. Kenenisa BEKELE
13. Roger FEDERER
14. Carolina KLÜFT
15. Rafael NADAL

Just a question: How do you guys define "great" athletism? IMO a great athlete doesn't only define himself by talent or abilities that make him stand him out from others but also by continuous improvement and the will to go until the maximum to get even better.
Don't get me wrong: Ronaldo and Maradona were great footballer but all time great athletes? Certainly not, especially not Maradona who basically did everything possible outside the pitch to limit his physical abilities. I'm no personal fan of him but if there's one footballer who deserves to be here, then it's CR7.
Anyway, although I certainy will miss some great names here, here's my top 15 (without any special order):

Daley THOMPSON (IMO the greatest athlete ever who both competed and dominated in the most challenging sports discipline, I'm surprised that no one mentioned him here before)
Michael PHELPS
Carl LEWIS
Emil ZÁTOPEK
Eddy MERCKX
Usain BOLT
Martina NAVRATILOVA
Cristiano RONALDO
Michael JORDAN
Ole Einar BJØRNDALEN
Wayne GRETZKY
Muhammad ALI
Michael SCHUMACHER
Jim BROWN
Roger FEDERER

But as I said above there would be plenty of other names who could be mentioned here.

I personally thought that this ranking wasn't just about great athletes but also athletes who somehow, for any reason, we are attached to or marked a specific time of our lives.

Who created this topic should have defined whether we should post our favorite athletes or the ones who we consider the best athletes in history. In my case, those two lists are very very different.