Mourinho led Los Blancos to a La Liga title and a Copa del Rey triumph during his time in the Spanish capital, and the Blues boss accepted that Ronaldo was key to his team in Madrid.
He told Telefoot: "He is what Zinedine Zidane is to the French. He is an incredible player – a goal machine. I don't need to tell you what everyone already knows.
"I must remember a kid who is a goalscoring machine, who helped me to be champion, to win the Copa and the Supercopa. Probably I also helped him — we all helped each other, mutually, to win the title with 100 points against the best Barcelona team in history."
Ronaldo, who won the Ballon d'Or back in January, is expected to be one of the favourites for this year's award when the nominations are announced later this month.