It's fun to watch an athlete, knowing that he is one of the all time greats in his sport. Michael Phelps has long since surpassed Mark Spitz to become the greatest swimmer of all time. He may or may not win individual gold in Rio, but either way, his legacy is cemented.
Usain Bolt is the greatest sprinter of all time. No one else has ever won the Olympic double double, and Bolt has a slew of world championship titles as well. The margins by which Bolt broke the 100 and 200 world records were stunning, and it's hard to imagine anyone breaking those records any time soon. In any case, win or lose next week, Bolt's status is cemented.
Jesse Owens and Johnny Weissmuller qualify as legends because you've heard their names even if you're not a fan of their sport. (They "transcended" their sport, so to speak.) If you are a fan, names like these seem to acquire not just athletic significance, but almost historic significance.
Of course, Owens' name actually does have a historical tint to it, because he won in Berlin in 1936, where he was supposedly snubbed by Hitler. That turns out to be a complete myth, but it has stuck, because it has served an important propaganda purpose.
Johnny Weissmuller was probably more famous as the movie Tarzan than he was as a swimmer, but those two roles were inextricably entwined, and he is now a part of history.
Even in a sport like swimming, which doesn't have a big fan base in this country, there are names non-fans are at last vaguely familiar with: Duke Kahanamoku, Dawn Fraser, Don Schollander, Mark Spitz, Shane Gould, Janet Evans, and a few others. (This is a far, far smaller club than the official Swimming Hall of Fame.)
It's interesting to speculate which names from the current era will enter that smaller, more exclusive club. Michael Phelps is obviously already a member; Ryan Lochte probably is, too.
Katie Ledecky seems set to join that club. She's already set twelve individual world records so far; she'll likely set another in the 800 free in a couple days.
It's gratifying to see her thrive. She's tough, enthusiastic, hard-working, and unpretentious. She's also obviously competing clean: her progression was rapid but steady, and she won her first Olympic gold as a 15-year-old. She's big and strong, but her body is obviously not molded by steroids. And she never had a sudden spike in performance in sync with a sudden, suspicious change in build.
Ledecky is a slight favorite to win the 200 tonight (Sarah Sjostrom could provide stiff competition), and she should easily win the 800 in three days. Ledecky's records should last a long time, possibly even longer than Janet Evans's 17 year run.
Today she's the young wunderkind; in twenty years, she'll be a legend. Even non-swimming fans will likely be at least vaguely familiar with her name.
Update, next day: three out of three commenters have now told me that they've never heard of most of those "legendary" swimmers. Looks like I'm dead wrong about them being household names.