Michael Jordan came back to the Bulls after baseball and was an absolute hero. He led Chicago to three championships and went from Hall-of-Famer to Best Player Ever.
Jordan also came back one too many times when he joined the Wizards. It was ugly. He wasn't the same guy, and the lasting image was him front-rimming a dunk he couldn't put down in the All-Star game. Yikes.
Hopefully Lance Armstrong will be different, despite returning to professional cycling to win his eighth Tour de France this summer. His first competition? Australia. His performance after Day One? Down under (Get it?).