So in five years time, who will we be talking about? A 30 year-old Messi still relying on his God-given talent, or a 32 year-old Ronaldo, whose game has come from hard work on the training pitch?
Of course, Ibra was exaggerating. Natural talent is one thing, but Messi's ball control at top speed didn't come from the heavens. It was developed first on his home street in Rosario and then at Barcelona's famed La Masia training complex.
But has Messi and the Barca coaching staff focused too much on his strengths? As Ibra says, where's his right foot?
"Messi does not need his right foot, though," Ibrahimovic conceded. "He only uses the left and he's still the best in the world!
"Imagine if he also used his right foot ... Then we [Milan] would have serious problems!"
But in comparing the roads of Messi and Ronaldo, Ibrahimovic does highlight what could lie ahead for both players.
For the moment, Messi is head and shoulders the best player on the planet. But it's all come natural to him. There's no evidence of hard work on the training pitch. No right foot, no great ability at free-kicks - can the Argentine continue to be successful relying on his pace and ball control?
Contrast this to Ronaldo's approach. At Manchester United, Sir Alex Ferguson actually took the then winger aside and pushed him to make more of his 6ft 1in frame. Hours upon hours were spent at Carrington improving Ronaldo's heading. The leap and the timing in the air that we all see from Ronaldo, now in Real Madrid colours, didn't suddenly happen - it was a skill built from the ground up at United.
His former United teammate Edwin van der Sar recently said: "Cristiano Ronaldo used to say that he wanted to be the best player in the world and probably a lot players say that, but he’s someone who really worked on it. During training he was unbelievable, just ran to the ball every time and make those actions."
And what of Ronaldo's free-kick technique - which he actually discovered playing table tennis. The Real star has created a new way of taking set pieces - which was celebrated at Wembley by Chelsea midfielder Frank Lampard when he produced 'a Ronaldo' against Tottenham. The Portuguese now has the game's greatest copying his inventions - can we say the same of Messi?
Phoenix Suns basketball star Steve Nash, who has a stake in the Vancouver Whitecaps and is close to many footballers, recently tweeted after one round of Liga games: "Cristiano Ronaldo 2 goals, Messi 2 goals, but a football wiseman said once: 'I don't care if Ronaldo does 6000 sit-ups, because he'll never be as good as Messi'. True?"
Nash, rather mockingly, was making fun of past reports of Ronaldo doing 3,000 sit-ups a day. It's actually part of a fitness regime designed to protect him from the groin injuries he suffered in his early years at United.
But the Canadian, like Ibrahimovic, was underlining why Messi will be starting from a long way back if he is to match Ronaldo in the latter years of their career.
Think of how many rivals Ronaldo's former United teammates Ryan Giggs and Paul Scholes saw off during their careers. Great players come and go, but Giggs and Scholes became icons because they could adapt and improve other parts of their game as their natural abilities began to wane. It's arguable that both players didn't truly peak until they were well past 30.
And would we still be talking about them as we do today if Scholes and Giggs had faded away at 31 or 32?
For Ronaldo, you can see him doing the same. The pace may go, but if he still has the desire, he can draw from what he's achieved on the training pitch to find new ways of staying competitive. For Messi, the evidence just isn't there.
To become an icon, it's no sprint. It's about longevity. And from what we've seen from both players up until now, in five years time, there'll be more people talking about Ronaldo as one of the greatest and not Messi.