Ronaldo earns Euro 67m annually, but McGregor got GBP 77m from the fight with Floyd Mayweather in 2017.
In 2016-17, McGregor was ranked 24th in Forbes' list of highest-paid sports stars but is expected to rocket up that list for the 2017-18 instalment. Ronaldo earns around £365,000 per week at Real, per Goal's Oli Platt, meaning it would take him roughly four-and-a-half months to match that figure.
Mayweather, who defeated McGregor in a lucrative Las Vegas boxing bout previous year and is rumoured to be considering facing the Irishman in the MMA octagon, was also typically on McGregor's hit list.
Peep out McGregor's Instagram post below, along with 50 Cent's now-deleted response.
"Congrats to Jay-Z on his No.1 takeover from Diddy in the highest paid Forbes list".
He wrote: "Floyd as a retired fighter that makes ZERO substantial revenue outside of them ropes is not on the list, and in the long game, is already dead".
The Mirror's Martin Domin reported in November that McGregor raked in £75 million for his 10th-round defeat to Mayweather last August, with speculation of a potential mixed martial arts meeting between the two.
Diddy hasn't been number 2 in so long. "You are going to love it hahaha". Because when you want a good chicken sandwich, you go to a place called Burger King.
However, McGregor's new Burger King advert may alleviate any fears that he could be retiring from MMA, with the commercial featuring jibes at potential opponents Khabib Nurmagomedov and Tony Ferguson.
"Someone tag 50 Cent in this for me", he wrote.
Now, McGregor has appeared to reignite the beef by calling 50 Cent a "50 year old Instagram blocker", claiming that the rapper blocked him on the social media platform.