Exceeds expectationsLike the other greats, Phelps rarely fails to meet the ridiculous expectations set before him. Better yet, he exceeds them. Skeptics, for example, thought he might have hit his peak at last year's world championships, where he won seven gold medals and set five world records. Too bad, they figured, that he did it at an event seen by few in the United States.
But great athletes are always upping the ante, creating possibilities for themselves that we could never fathom. Phelps was clearly in that realm last week, as he swam a full body length ahead of those little green bars that NBC uses to track world-record pace.
Another said, "I don't know, but I bet he'd be great."
It was a silly moment, but it illustrated the mentality Phelps has created. Put him in water and it seems nothing is beyond him. If he lined up to race a dolphin or, heck, Poseidon, would you bet against him?
"At his level, the amazing thing is not the pressure he faces but the physical demands of it," Deford said. "Woods or Federer have to play the same amount as everyone else to win a tournament. But this guy is, in effect, a racehorse with a weight handicap. Nobody else is doing the schedule he's doing, but he's still beating them."
Inspiring other greatsLike Woods, Phelps has taken a sport that was never considered cool and made it fascinating to other great athletes. LeBron James made it known that Phelps' record swim in the 400-meter individual medley inspired him. Carmelo Anthony compared the swimmer to a shark in The New York Times.
James, Anthony, Kobe Bryant and Dwyane Wade led cheers for him the night he won his 10th and 11th career gold medals.
"To be able to watch that kind of greatness in person is something I'll always remember," Wade wrote in his Olympic diary for the Associated Press.
Dorfman said Phelps has transcended swimming, a sport ignored by most Americans between Olympics.
"He's beyond the normal jock at this point," he said. "He's a superhero. He's Aquaman."
Some of Phelps' swims have the Bunyanesque quality of Wilt Chamberlain's 100-point game or Bob Beamon's record-setting long jump in 1968, feats that seemed more aligned with fable than with previous standards of human performance.
He can handle adversity, as he did when water poured into his goggles early in the 200-meter butterfly Wednesday morning. A blinded Phelps broke his own world record anyway. It was reminiscent of Muhammad Ali, blinded by liniment in his eyes, surviving the fourth round so he could take the heavyweight title from big, bad Sonny Liston in 1964.
Phelps has also stood the test of time by dominating two straight Olympics, something no other performer has done in so many events. He is kind of like Jordan, who put himself in the greatest-ever argument by winning three straight championships but then put the cherry on the sundae by returning from a two-year layoff to win three more.
If numbers are your thing, Phelps stacks up pretty well there, as well, having won more gold medals than any other Olympian in history.
The other sideSo he has a lot going for him in these crazy debates. But it is possible to construct an argument against Phelps.
He doesn't have to worry about the natural elements, shifting course designs and huge fields of competitors that torment Woods week after week in golf.
Unlike Jordan or Federer or Graf, he is able to train in relative anonymity and has never had a competitive target on his back night after night for many years.
If you want to bring Wayne Gretzky or Joe Montana into the mix, you could argue that Phelps has never had to deal with huge men careening at him in hopes of wrecking his remarkable body.
If you want to talk other Olympians, maybe Carl Lewis was more amazing because it's so rare for someone to be the best at jumping and sprinting.
No science can lend answers to these questions. The fun of it is that Phelps has put himself in the conversation.
"I guess people in Baltimore will be asking, 'Who's greater, Babe Ruth or Michael Phelps?'" Deford said. "You just throw away the dictionary on this one. There's nothing you can say. It's one of a kind."
Sun columnist Rick Maese contributed to this article.