The Portuguese winger enjoyed a fantastic opening against Roberto Mancini's side; and after ten attempts at beating Joe Hart, the former Manchester United player netted a dramatic 3-2 winner in the 90th minute.
All five goals arrived in the final 20 minutes of an encounter that could have easily swung either way. While Marcelo, Angel Di Maria and Xabi Alonso all performed fantastically for the La Liga champions, Ronaldo stole the show.
Mourinho's tactics are always shrewd and once again paid dividends on the pitch.
The decision to drop Mesut Ozil, Karim Benzema and Sergio Ramos seemed ludicrous before the match began; but before long, Madrid's usual swagger had City on the defensive.
Ronaldo threatened from the left wing, forcing Hart into an excellent save. Minutes later the England number one was called into action again when Ronaldo's strike cannoned off Gonzalo Higuain's head.
Mancini's men were unambitious in the first half. His side could have easily gone into the break at least 2-0 down.
Hart played admirably in the opening 45 minutes and kept his team in the toughest test of their Champions League group.
As the second half progressed and City came forward, it looked as if Madrid were slipping to their fourth defeat of the season. Edin Dzeko's goal perked Mourinho's side into action as the influence of Ronaldo shone through.
Only one player on the pitch looked as if he could stop the winger. Vincent Kompany managed to quash Ronaldo's threat during the latter stages of the first half. The Belgian's positioning and strength is so often key to City's success, but as the game rolled on, Kompany and his fellow defenders failed to close the opposition down.
Neat interchanges between Ronaldo and Marcelo caught Maicon napping. The former Inter Milan player's legs looked as if they were creaking before the match finished, echoing his display against Gareth Bale in 2010.
While his goal will grab the headlines, Ronaldo's overall performance was impressive for a player under such intense scrutiny.
Since he revealed he isn't happy at the club for "professional reasons", media attention has followed his every step with increasing eagerness (via The Sun).
The Madrid talisman posted an unbelievable set of statistics against City. Each of his 50 passes successfully found a teammate. He also won 100 percent of his aerial battles and provided three key balls throughout the match.
With the score at 2-2 was anyone else going to score the winner? Kompany may have ducked out of the way, but Ronaldo fully-deserved the glory.
After the match Mourinho said his team has its DNA back (via Yahoo! Sports). Both the 49-year-old and Ronaldo ended up on the floor out of celebration.
If the two continue to work in such unison the rest of the Champions League contenders must watch out.