Lionel Messi or Cristiano Ronaldo? Whatever one's thoughts of the legitimacy of the comparison, there is no denying that it is a question which has defined a generation. Everyone picks one or the other. Well, almost everyone.
In Deco, one could not hope for a more impartial judge, and when the former Portugal and Barcelona midfielder was asked for his preference in the summer of 2016, he found fault with the question.
"Ronaldinho was far more gifted than Leo or Cristiano," he countered. "He was a natural with special ability. Whenever we gave the ball to him, the moves and goals were from a different world."
It is difficult to disagree. After Ronaldo (the Brazilian version) had changed the entire perception of what a No.9 could do, Ronaldinho came along and changed the entire perception of what a footballer could do.
He brought the tricks and flicks of futsal to a full-sized football field. He pulled off pieces of skill that nobody had seen before.
Kevin-Prince Boateng tells remarkable tales of Ronaldinho hitting the crossbar three times in a row in training just because he could. "We wondered how it was possible there was so much talent in one body," he gushed.
Eidur Gudjohnsen, meanwhile, became convinced that Ronaldinho was capable of defying the laws of physics.
"When you play with him and see what he does with a ball, nothing surprises me any more," the former Barca forward admitted. "One of these days, he will make the ball talk."
He could certainly do anything he wanted with it but, as Brazil and Real Madrid legend Roberto Carlos pointed out, "it wasn't just about the tricks - he created and scored the goals to match his ability."
Indeed, his stunning strike against Chelsea at Stamford Bridge in 2004, from a standing position, was the most exhilarating, bewitching and bemusing illustration of him marrying skill and substance.
In truth, there were innumerable examples of his outrageous ability. Indeed, Ronaldinho became a human highlight reel; an entire generation watched Barca games just to see what he could, and would, do next.
Because of a scheduling dispute in the lead-up to an international break, his Blaugrana debut, against Sevilla, kicked off at five past midnight on September 3, 2003.
In spite of that, 80,000 supporters still flocked to Camp Nou to see their new Brazilian superstar. Not one regretted that decision.
At around 1.30am, Ronaldinho picked up the ball inside his own half, skipped past two opponents and then unleashed a stunning 30-year drive that crashed off the crossbar on its way into the net. Barca drew the game but Ronaldinho had brought hope back to Barca. In time, he brought trophies too.
David Beckham once said, "There was a period in Ronaldinho’s time at Barcelona where he was almost unplayable." It was between 2004 and 2006, when Barca won back to back Liga titles, as well as the Champions League.
During that two-year spell, Ronaldinho was at the peak of his powers, as motivated as he was magical. Consistency coupled with genius saw him attain a level of play that only the likes of Alfredo di Stefano, Pele, Johan Cruyff, Diego Maradona and Lionel Messi could be said to have equalled.
On a weekly basis, Ronaldinho did things that took that breath away – and all the while with that endearingly toothy grin on his face.
Frank Rijkaard enthused, "He transmits a lot of joy and pleasure playing the game, and he has individual skills that are of such a high level that everybody in the world adores him."
He wasn't wrong, either. Even some supporters of Barca's bitter rivals Real Madrid could not help but stand and applaud when he tore their beloved Blancos asunder on a famous night at the Santiago Bernabeu in November 2005.
Ronaldinho admitted afterwards, "I will never forget this because it is very rare for any footballer to be applauded in this way by the opposition fans."
Indeed, the only previous Barca player to have been given a standing ovation at the Bernabeu was Maradona. Messi, despite his numerous masterclasses in Madrid, is still awaiting his, which is sadly indicative of the current era.
The partisanship, the rivalries have become too bitter, too toxic. One is either Barcelona or Real Madrid, Messi or Ronaldo - one cannot appreciate both, apparently.
Ronaldinho, though, transcended the traditional lines of tribal warfare. He was above competition. He wasn't driven by being the best. He just wanted to have fun.
From his demeanour, his behaviour, it was obvious that he didn't just enjoy football, he enjoyed life, and he just wanted others to enjoy it too.
When Barcelona travelled to Los Angeles in the summer of 2006 for a couple of pre-season friendlies, basketball legend Kobe Bryant attended one of the Catalan club's training sessions.
"Ronaldinho was a good friend of mine," the American reminisced a couple of years ago. "And while I was talking to him, he told me, 'Kobe, look, I'm going to introduce you to the guy who's going to be the greatest player of all time.'
"And I said, 'What? You're the greatest!'
"And he said, 'No, this kid right here is going to be the best.' And that guy was Lionel Messi and he was only 18 or 19 at the time."
Ronaldinho was both humble and humorous. Many felt he didn't take the game as seriously as he should have done; that he wasted his talent, which is both staggering and scary when one considers that he won a World Cup, a Copa America, a Copa Libertadores and a Champions League.
Nonetheless, he is often asked about his regrets, and that will become an increasingly common question now that he has decided to call time on his professional career.
However, he insists that he has only one. "I would have loved to have played more with Messi, he's a great player and I'm very glad to have helped him at the beginning of his career with the assist for his first Barca goal," he revealed.
"Having seen him go on to become such a great player, it would have been fantastic to have played more with him, but at that time my period at Barca was over and it was time for me to move to achieve new things and set new objectives, so the time had come for me to leave."
Now, the time has come for him to walk away from a game that he enriched with his skills and his smile.
Sure, he could have won more trophies, and could have claimed more Ballons d'Or, but he is rightly proud of his career: "I've achieved everything I wanted to and I'm grateful for that."
In truth, it is we who should be grateful to him. In this modern era of corruption, greed and negativity, Ronaldinho reminded us that football can still be fun; that the game can still be beautiful; and should always be played with a smile upon one's face.
There is no greater legacy than that.