I'm not sure that success in a sport (or sports) always equates to how athletic a person is. A lot can go into judging how athletic someone is. Speed, strength, size, agility, eye/hand coordination,...anything.

A few relatively recent outstanding athletes, looking mainly at overall athleticism:

Georges St Pierre
Luke Kuechly
Mac McClung....really young
Johnny Manziel
JJ Watt

Plenty of previous, I just looked at recent....