Ronaldo visited the UFC lightweight champion in training and the Irishman quipped: 'You were number one on the Forbes list, I was like number 35 or something. I'll get up. Maybe next year I'll get you.' Ronaldo replied: 'I don't think so.'
McGregor will still not be on top of the athlete rankings, with Mayweather's purse superseding his earnings. Some reports claim that 'Money' is in line for £233m from the lucrative Las Vegas clash.
But both men can expect to overtake some huge names in the world of sport such as LeBron James, Roger Federer and Lewis Hamilton.
And now that 'Money' has retired, appropriately on top of the financial rankings, McGregor will fancy taking top spot in the coming years.
The Irishman is an active champion in the UFC and is even open to the possibility of another contest before the end of the year.
As the organisation's premium pay-per-view lure, McGregor's fights continue to break records for Dana White both in terms of gate and broadcasting revenue.
And at only 28-years-old, the 'Notorious' has plenty of pay days left in him.