There was speculation during the summer that Ronaldo could be set to leave Real Madrid and return to Old Trafford, having spent six years with the club before he moved to the Santiago Bernabeu in 2009.
A move did not materialise and Ronaldo instead signed a five-year contract with Real, insisting that he would be happy to spend the rest of his career in the Spanish capital.
It seems highly unlikely that Moyes will now ever get his wish to manage Ronaldo, but he is still hopeful that it could happen.
"Everyone at Manchester United would tell you he is the best in the business anyway," Moyes told MUTV, having watched Ronaldo's awesome performance for Portugal in their World Cup play-off victory over Sweden in Stockholm on Tuesday.
"I have not been fortunate enough to work with him but there is still hope some day it might be possible."
With FIFA extending the voting period for the coveted Ballon d'Or prize, it seems likely Ronaldo will claim a prize he won for the first time as a United player in the 2008 Champions League campaign, when he scored an incredible 42 goals.
Former team-mate Anderson is also in no doubt about whether the man from Madeira would be welcome back in Manchester.
"When you have Ronaldo it makes it easy," said the Brazilian.
"He scores all the time. He scored three goals on Tuesday. He is an amazing player, for me the best player in the world."