His tantrums struck a populist chord, immortalised by the rhetorical question "You cannot be serious?" to umpire Edward James in a 1981 Wimbledon match against Tom Gullikson.
That's not to justify what was sometimes sheer bullying of chair umpires or poor sportsmanship to opponents, but his brand of entertainment captivated fans.
McEnroe's scrutinous nature saw him morph into one of tennis' most respected commentators as networks sought what he refers to as "a more informal style".
In an area where exponents can become slaves to sycophancy, McEnroe's analysis exudes a degree of independent thought that reminds you why he was such a driven youth.
In his latest autobiography But Seriously, the sequel to 2002's You Cannot Be Serious, he continues to grapple with the establishment. Take the description of when he won Wimbledon on the first of three occasions in 1981.
"They were practically choking on their cucumber sandwiches at having someone like me, the mouthy kid from Queens (we're talking the New York borough, not the exclusive tennis club in West London), become a member. They were scared as hell at the thought of me propping up their bar. Don't worry, guys, I'd rather have chewed my headband than show up for a beer in SW19."
The concept of bowing and curtsying to the royal box is also dispatched with a firm forehand.
"This was the class system gone mad, the opposite of a meritocracy where hard work is rewarded and people are respected because they've actually done something, not because they've been born on the right side of the tracks.
"Who were the performers here? The players, right? So why were they bowing to someone else when they were about to provide the entertainment? Those people in the royal box should think about bowing to them."
He still courts controversy among the offenderati. In the book's promotion he was asked by an interviewer whether Serena Williams was the best player in the world.
McEnroe, who has long supported pay equity in the sport and recently described himself as "proud to be a feminist", responded by saying "she'd be like [number] 700". Cue a maelstrom of criticism for speaking his mind.
Yet his habit for honesty has won more friends than enemies.
"As a player, I think people respected my effort and energy and trying to stand up for myself," he tells the Herald from London ahead of Wimbledon.
"They weren't used to something like that, at that time. Some of my decisions were dumb in terms of how they affected my career - it's tough to know when and how much to blow off steam - but I've been lucky enough to meet some tremendously talented people who respected me.
"As a commentator, they might've seen a different side which was someone who didn't take himself so seriously. I think they think of me as someone they can relate to. I'm someone they might see on the street, a fairly normal person who does one thing well.
"At the peak of my career, a lot of tennis people were saying 'ban McEnroe for a year, his behaviour's outrageous' but then guys like Mick Jagger and Jack Nicholson were telling me 'don't change a thing'. Who are you going to listen to?"
VICTOR HUGO, in Les Miserables, wrote "the supreme happiness of life is the conviction that we are loved".
At 58-years-old and a father of six, McEnroe appears to have blossomed under this premise with Patty Smyth, his wife of 20 years.
She accepted his faults and offered him the freedom to continue his career without rancour.
Smyth, a musician, summons a line from Gladys Knight and the Pips' Midnight Train to Georgia to encapsulate the success of their relationship: "I'd rather live in his world, than live without him in mine".
"At the end of my first marriage [to Tatum O'Neal in 1994] things weren't looking great," McEnroe says.
"I've had a second chance, and feel fortunate that I was smart enough to take advantage. Patty's allowed me to be me. She'd try to do the best with the kids when I was away.
"She's allowed me to explore different things in my life; not all succeeded, but they allowed me to continue to find myself."
The book concludes with a 2004 tribute from daughter Emily. The epistle includes details like her Dad's ability to slice a mean grapefruit each morning. Such a poignant touch hints this is an area of his life in which he seeks as much perfection as his tennis.
He was brought up as a Catholic, but raised his children in a largely secular environment.
"I didn't opt out of Catholicism because of my kids, I opted out beforehand. I didn't push my kids [into religion] but I worry sometimes if I went too much the other way."
He's also tried to vaccinate his children against what he describes as the "affluenza" contracted from the wealth amassed in his profession.
"It can be tricky for kids to grow up with people who are well-known and successful. My ex-wife won an academy award at 10 [history's youngest in Paper Moon] and had success, just as my present wife has. We were lucky enough to afford a nice place in Manhattan, which was always the dream after I grew up in Queens. It's easy for the kids to get a sense of complacency.
"It's always a trick to motivate kids so they feel secure and loved. I tried to do the best I could, but it's difficult to juggle sometimes."
Listen: John McEnroe talks to Andrew Alderson
McENROE HAS firm views on changing the game to embrace its grassroots.
"The biggest problem is that we prevent people from trying [tennis]. In the New York area where I live, the cost of real estate has gone up and forced tennis clubs to shut down and get replaced by office, apartment and garage buildings. That issue needs confronting.
"That's why I'd encourage kids to stay in college, and let the top players use scholarships to give them time to grow as people. You don't want them forced to go on tour and get sponsorship where they can lose money before they make any."
McEnroe says playing tennis should not come at the expense of doing other sports.
"Studies show kids might end up getting hurt if they focus on one sport from an early age. They can overdevelop certain muscles and become susceptible to injury.
"I know playing basketball and soccer as a teenager helped me. Playing with other kids develops friendships and character. You don't want kids at age eight saying 'that's the only sport I'm going to play'. That's not helpful mentally or physically.
"It's just like I don't believe in home school, especially for tennis people, because kids are so isolated to begin with."
McEnroe would like the game sped up at the top level.
"The average attention span is shorter these days, so we have to look at the length of matches. At the very least we need tie breakers in all fifth sets.
"You could speed up a match without lets on serve. There would be luck involved, but the entertainment value would be better."
McENROE IS back for another edition of Wimbledon, the venue of his first major breakthrough when he reached the semi-finals 40 years ago.
"That changed my life," he says. "Then, when I won it in 1981 [after the umpire outburst], I had a tough time dealing with the pressure. The media were coming after me - and I know some of it was deserved - but I was having a hard time registering it. When I won, the feeling was so great it made me want to do it again."
The pursuit of winning, or more accurately learning, and the selfishness required to do so, is a theme of the book.
The prologue recounts his experience waking up at 5.14am on June 8, 2015 after a nightmare featuring his five-set loss to Ivan Lendl at the 1984 French Open. He subsequently attempts to right "the wrong" in various exhibition matches.
The simple advice would be "let it go" but that's not how McEnroe's wired.
Wife Patty sums it up by describing how he inadvertently didn't talk to her on a trans-Atlantic flight to Paris after they had been dating a couple of months. It was an early dose of his intensity.
"But one of the great things about him is that he will take direction," she writes. "He always wants to be better at everything... that's part of his DNA, wanting to learn, and I find that very attractive in him, because a lot of people aren't like that, especially as they get older.
"If you asked me something about him that could be improved, it's that even now, he's a little self-centred... that's been a hard habit to break."
Yet that probably encapsulates why he can grow on you. There are traces of him in most of us. Few are immune from "doing a McEnroe".
A set of Serious facts on John Patrick McEnroe
1. His favourite match is not his 1983 Wimbledon final victory against New Zealander Chris Lewis, but the same occasion in 2008 when Rafael Nadal triumphed in five sets over Roger Federer at nightfall, pre-roof.
2. McEnroe enjoys an interest in art dealing and holds respect for the way Damien Hirst, Takashi Murakami, Richard Prince and Jeff Koons operate.
3. He plays the guitar (wife Patty says he "wrestles it into submission"). His favourite axeman is Eddie van Halen, but he has regularly hung out with other musicians like Chrissie Hynde, Paul Simon, Robert Plant and the Rolling Stones.
4. Jerry Seinfeld lives in McEnroe's New York apartment building on Central Park West. Seinfeld once said McEnroe was the building's most famous resident... until he arrived.
5. One of McEnroe's favourite fashion statements, which he still sports on occasion, is a full denim jacket and jeans ensemble, otherwise known as "The Canadian Tuxedo".
6. A candidate for "quote of the book" comes when McEnroe, seated on an Idaho chairlift with skiing buddy Arnold Schwarzenegger, tentatively asked what his pal said to then-wife Maria Shriver straight after a story emerged about The Terminator groping women. Schwarzenegger allegedly boomed: "I told her 'Maria, you must have weiner schnitzel on the table at six o'clock!'"
