The debate of who the better player is has been raging for the last decade.
The Portuguese star looks set to win a league title in a third country after three Premier Leagues with United and two La Liga titles.
And the 34-year-old has won the Champions League four times, accompanying five Ballon D’Or honours.
But the forward has always had Messi for company.
The Argentine, who has spent his entire career at Barcelona, has won nine La Liga titles and four Champions League.
With five Ballon D’Ors to the 31-year-old’s name also, there has ben nothing to choose between these two stars.
And Mourinho, who worked with Ronaldo at Madrid, believes this is a good thing.
It comes as:
Speaking on RT, he said: “I think they are lucky and unlucky to be in the same generation.
“They are lucky because they can compete against each other.
“They look to each other in a positive way and get extra motivation.
“If there was only one of them, they would have 10 Golden Boots.”
But the Portuguese manager went on to give a warning for the future.
“Now, I think they have put the bar really high,” Mourinho added.
“And you have the players coming behind, who I like to call the ‘little monsters’.
“The bar has to be high, so it has to be incredible motivation for Neymar, [Kylian] Mbappe and [Antoine] Griezmann.
“Unfortunately, Cristiano and Messi will not last forever.”
And viewers were full of praise for Mourinho’s assessment.
“Mourinho is the greatest,” one said.
Another commented: “Jose should have his own show.”
While a third suggested an even higher honour for the former United boss.
“Sir Mourinho,” they said.
This comes as former United coach Rene Meulensteen revealed on difference between the Portuguese coach and Sir Alex Ferguson.