A hundred years from now, it will be easy for anyone with an interest to understand the greatest of — for example — LeBron James, Tom Brady, Wayne Gretzky and Aaron Judge. Just go watch the tape.

Joe Jackson was on his way back from the golf course in Simpsonville, S.C., when he heard the news. “I was driving home and my phone started vibrating a lot,” he said. “The first stop sign I got to, I ...