Some people become legends for a legendary feat.
Bob Beamon fits into that category. Before his leap at the Mexico City Olympics in 1968, the world record in long jump had taken 40 years to grow by 55cm. Beamon added that much again in one jump with his world record of 8.90m.
Like Beamon's jump that set the standard for the next 23 years, Bolt's world records in the 100m and 200m made the seemingly impossible suddenly very real.
In London, it felt almost disappointing that Bolt didn't break his world records again. But even Bolt can't beat Bolt every time.
His 100m in London, at 9.63s, was the second-fastest ever. And his 19.32s in winning the 200m was as fast as Michael Johnson ever ran it. Many thought the American's world record from the 1996 Atlanta Games was safe until Bolt sliced a couple of hundredths off it at the Beijing Olympics in 2008. Then, a year later, Bolt cut that mark to a mind-boggling 19.19s.
Other legends, like Jesse Owens, were products of their time. Owens' four Olympic golds were one fewer than Bolt now has. But the legend of Owens rests largely on the fact that he was a black athlete and his winning at the 1936 Berlin Games made a mockery of Adolf Hitler's theories of white superiority. Unlike Owens, Bolt's colour isn't a big part of what makes him legendary.
Jacques Rogge, the IOC president, thinks it's too early to crown Bolt a legend.
"The career of Usain Bolt has to be judged when the career stops," he said. "Let him participate in three, four games, and he can be a legend. Already he's an icon."
But Rogge was a Bolt party pooper in Beijing, too, saying he should "show more respect for his competitors and shake hands."
Rogge didn't get it then, and doesn't seem to get it now.
Bolt is manna for the Olympics and for sport. Not only a superior athlete but charming, funny and, as far as we know, not doping. He loves the crowds and they love him back. In the 80,000-seat Olympic Stadium, they chanted "Usain! Usain!" They didn't do that for other athletes.
After the 100m on Sunday, they yelled at him: "Do the Bolt!" He didn't get irritated, he didn't ignore them. He pointed his finger at the sky in his trademark pose, happy to please.
He also stopped a television interview in midflow because the "Star-Spangled Banner" was playing in the stadium for Sanya Richards-Ross, winner of the women's 400m. How's that for respect, Mr Rogge?
Really, the Olympics couldn't ask for a better champion.
"Everyone owes him a debt of gratitude," said two-time decathlon Olympic champion Daley Thompson, "because he's the guy who's bringing the crowds back."
The Oxford English Dictionary is more helpful than Rogge in trying to understand Bolt's "legend" claim.
It says the word can mean "an extremely famous or notorious person". Few people on this planet are more famous than Bolt.
But it can also mean "a story," something recounted over and over.
And that fits Bolt perfectly.
For years to come, we'll talk not only about his Olympic triumphs, but about the way he won them. The magnificence of him erupting from the blocks and unfurling his muscular 1.95m frame. The sight of his long legs gobbling up the track. On the biggest stage, he made us gasp, not once or twice but repeatedly.
The best there ever will be? Even with Jordan, no one can really tell.
But Bolt is the best sprinter there ever was. Everything he is and everything he has done are stories that will be told and retold.
And that, like Jordan, Owens and others, is why Bolt is now a legend.
