I think tennis is boring, but McEnroe is fucking amazing because of his tantrums and because he started learning tennis in his 20's. Which means his repeated victories were powered completely by unadulterated rage and had nothing to do with training.
Wikipedia: "McEnroe grew up in Douglaston, Queens and started playing tennis when he was eight years old at the nearby Douglaston Club with his brothers."
I remember him from when I was a kid. I still don't know anything about tennis except that John McEnroe threw the absolute best tantrums ever. Watch and learn, kids.