The veteran forwards have won 12 Ballon d'Or awards between them as well as nine Champions League titles.
And while they are now playing their careers outside of Europe, they remain in sparkling form.
World Cup winner Messi has scored 11 goals since joining Inter Miami in the summer, with Euro 2016 champ Ronaldo firing in nine times for Al Nassr this season.
But despite over 1,500 goals between them, Manchester United legend Ferdinand, who played alongside Ronaldo, overlooked the pair when naming his GOAT athletes.
Speaking to Sports Illustrated, the 44-year-old was asked to pick his four sporting GOAT stars of all time.
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Opting not to name a footballer, the TNT Sports pundit selected two boxers, a basketball legend and a certain Swiss tennis icon.
He said: "Muhammad Ali, Mike Tyson, Michael Jordan, Roger Federer."
Despite not including Messi or Ronaldo, he remains huge admirers of the pair having repeatedly waxed lyrical over the duo in recent years.
Ferdinand defended Ronaldo over his move to the Middle East earlier this year, while he described Messi as an 'alien' following his mesmeric World Cup displays.
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Speaking to Goal in 2019 of the pair, Ferdinand said: "We are blessed that we are in the presence of these two amazing footballers and it doesn't matter if you think one is better than the other at this stage.
"They are both just ridiculous talents and what puts them so far ahead of everyone else is their mental strength.
"That area of their game never ceases to amaze me and separates them from everyone else. It is something I marvel at, definitely.
"To consistently want to do what they have done at that level for so long is not something many people have and, when you throw in their talent, it's an incredible combination."