Terry Fox is on youtube.com
Although I agree that most of what he does today is for publicity, I would have to say that anyone that can complete the Badwater Ultramarathon is an exceptional distance runner (although they may be crazy), to win it puts them well above 99.9% of the rest of the ultra runners in the world.
That was not the comparison being made in the quote in the original post. Michael Jordan is the best basketball player the sport has seen (to this point; LBJ may prove to be better eventually) but Karnie is not the best runner, distance runner, or even ultrarunner to grace the face of the planet. Not even close.