Jose Mourinho's side were on the verge of crisis after a dreadful start to La Liga and the Portuguese coach had launched a stinging attack on his players in a bid to stun them into life for their opening game in Europe's elite club competition.
Ronaldo's revelation two weeks ago that he was feeling "sad" for professional reasons and his refusal to celebrate goals had not helped but Mourinho's rallying call appeared to have the desired effect as Real stormed back to break City hearts.
Roared on by fans desperate for a return to winning ways, Real equalised first through Marcelo and then as late as the 87th minute when substitute Karim Benzema stroked the ball into the net just two minutes after Kolarov's strike.
The stage was set for the world's most expensive player and Ronaldo danced in from the left and unleashed a powerful shot that flew into the net under City goalkeeper Joe Hart.
"I celebrate when I have to celebrate," a jubilant Ronaldo, who has now scored 151 goals in 151 appearances for Real, told Spanish television.
"The match was very important for us and we are back in the fight," added the Portugal forward whose Champions League tally of 39 puts him level with former Chelsea striker Didier Drogba.
The clash in the Spanish capital was a contest between Europe's biggest spenders over the past four seasons and a thrilling encounter lived up to the pre-match hype.
City's Roberto Mancini fielded an unambitious formation with Carlos Tevez ploughing a lonely furrow up front with David Silva and Samir Nasri on the flanks in front of defensive midfielders Yaya Toure, Gareth Barry and Javi Garcia, a former Real player.
