Patrick McEnroe explained that the difference between Federer and some other greats like Sampras and Connors was that the Swiss player simply loved to play tennis.
Federer felt a huge joy anytime he was competing out there and it was less of a job for him. Everything came naturally which can't be said for many of the greats in the sport. Using the example of Connors and Sampras who were more business-like when it came to tennis, Federer was simply one who loved being on the court.
"A lot of players, I tell this to people all the time, some players love to win, Jimmy Connors, Pete Sampras. Roger Federer loves to win obviously, that made him one of the greatest ever, but he just... I don't think I've ever met anyone that just loved to go out there and just hit the ball around, a great player as much as him."
Federer ended up eclipsing both players in the hierarchy of great players and he's certainly the most popular player of all time.