Debates in football don't come much bigger than: Cristiano Ronaldo or Lionel Messi?

Contemporary football fans are blessed to watch the sport in an era where two of the greatest players in history are not only playing in their prime, but in the same country and at rivals clubs. One at Real Madrid and one at Barcelona, you simply couldn't write it.

Furthermore, with equally stacked trophy cabinets and five Ballon d'Or trophies apiece, it's almost impossible to separate the two and decide who the greatest truly is.

That doesn't stop supporters, managers and players formulating their own opinions, though, and it's a very intriguing debate.

More often than not, it surrounds Ronaldo's supreme work ethic against Messi's formidable natural talent but there's no foolproof way of deciding.

One of the closest ways we can come to deciding, however, is from speaking to the people who know both Ronaldo and Messi best.

There is an elite group of players that have managed to star alongside both players during their careers and, naturally, they've been asked to pick between the two.

Here's how these lucky players answered the question: 'who's best?'

Angel di Maria

Decision: Lionel Messi

Di Maria played alongside Ronaldo for no less than four years at Real Madrid as well as rubbing shoulders with Messi for Argentina. Nevertheless, he opted for his compatriot when asked asked in a January interview with the Spanish press.

“Messi is always the best, he's the best every year,” Di Maria answered, per the Daily Mail. “Cristiano Ronaldo's a special player, but Messi's from another planet.

“There are no words to describe Messi, he always surprises you.”

Carlos Tevez

Decision: Lionel Messi, just

"Messi plays another sport. For Messi to score three goals [in any given game] is normal."

Andre Gomes

Decision: Ronaldo and Messi

Gomes may give a clearer answer later in his career, but for the moment, he couldn't decide between his club and country's respective star players. The midfield stated: "I do not like to compare them out of respect.

"I will never answer it. I'm Portuguese and I have affection for Cristiano, as much as I do for Messi, who is my teammate at Barcelona."

Gerard Pique

Decision: Lionel Messi

Undoubtedly diluted by Barcelona bias, but Pique also spent four years playing alongside Ronaldo at Manchester United. The Spaniard takes no shame in lauding the Portuguese, but considers Messi to be the very best.

In one of his best quotes on the matter, he remarked: "For me it's like Messi is not human but Cristiano is the best of the humans."

Ezequiel Garay

Decision: Lionel Messi

Garay crossed paths with Ronaldo across his first two seasons at Real Madrid, yet couldn't help opting for his former international captain. That being said, Garay admits that he's held that opinion since the very first time he saw Messi in the Argentina youth ranks.

"When people ask me who is the best player ever, I say Leo," he explained.

"From the first time I saw him with Argentina U-15 to this day he continues to amaze me. He has no limit."

Henrik Larsson

Decision: Lionel Messi

When asked the question, he stated: "Cristiano is unlucky to be playing at the same time as Messi. Ronaldo is a very good player, but Messi is even better."

"He is from out of this world. He's so good that it's almost incredible. When you see him with the ball at his feet it's hard to believe that anybody else could do the same. He's a fantastic player to see."

Gabriel Heinze 

Decision: Ronaldo and Messi

Another player to sit on the fence, Heinze has never committed to a decision on who's the greatest despite national and club allegiances. He simply said: "Cristiano Ronaldo has drive and enviable self-discipline. He's an obsessive. As long as he has not reached the goal he has put in his head, he does not stop trying."

"Leo is inexplicable. Footballistically, he does not come from this planet. And as a person, he leads such a quiet life that is admirable."

Fernando Gago

Decision: Lionel Messi

It doesn't get more convincing than this. Gago played alongside Ronaldo at Real Madrid and with Messi for the national team, and thought the latter was just that extra level ahead.

He decided: "For me he [Ronaldo] is not number one. For me, the best in the world is Messi because of the way he plays, moves with the ball and changes matches.

"Messi has incredible ability and I love the way that he plays."

Deco

Decision: Ronaldinho?

Careers don't come much more stellar than Deco's and the Portuguese had a rather unique answer to the Ronaldo and Messi debate by actually suggesting that Ronaldinho was the most talented. He did, of course, have great praise for the current top two, however.

"Cristiano was young and athletic, very competitive. Messi worked hard to do what he can do with a football now at Barcelona," he explained.

"Ronaldinho was a natural with special ability. Whenever we gave the ball to him, the moves and goals were from a different world. He was far more gifted than Leo or Cristiano."

Who do you think is the GOAT - Ronaldo, Messi or someone else? Have your say in the comments section below.