Ronaldo, top scorer in the competition, took his goal tally for the season to 11 to make sure that Jose Mourinho's side went through to the last four 5-3 on aggregate despite losing the second leg 3-2 in Istanbul.
Mourinho praised the passionate support generated by the home crowd and the spirit of the Galatasaray players.
"We always want to play in an atmosphere like the one in the stadium tonight," he told reporters. "I don't think our players were affected by it but the Turkish players were really affected.
"They used the atmosphere in the second half and played a fantastic match. They were knocked out but if only all clubs would go out in the same fashion - they put their heart and pride into it."
Real went ahead on the night when Ronaldo slid the ball in from two metres following a low cross from the right by Sami Khedira after seven minutes.
Emmanuel Eboue then galvanised Galatasaray into action with a piledriver of an equaliser from the edge of the area in the 57th minute.
Wesley Sneijder made amends for a glaring miss moments earlier when he added a second goal for Galatasaray by sending the ball between the legs of Real defender Raphael Varane before supplying a neat finish.
Didier Drogba, Chelsea's hero in last year's final, then sent the noisy crowd into raptures with a delightful backheel following a cross by substitute Nordin Amrabat.
Real substitute Alvaro Arbeloa was sent off in the closing stages for a second caution but Ronaldo settled his team's nerves by adding his second goal in stoppage time after good work by Karim Benzema.
The Madrid team, who romped to a 3-0 win in the first leg at the Bernabeu, were in complete command after Ronaldo's seventh-minute goal in Istanbul.
The Portuguese almost doubled the lead with a long-range drive that keeper Fernando Muslera did well to stop.
Real winger Angel di Maria also missed an excellent opportunity after 24 minutes when a deft backheel from Ronaldo sent him through on goal and Muslera kept the ball out with an instinctive save.
Despite the raucous support of the home fans, Galatasaray were unable to make much of an impression early on.
It was only in the latter stages of the first half the hosts began to exert any meaningful pressure.
Diego Lopez saved well when Sneijder fired in a shot from the edge of the area in the 38th minute and soon after Drogba just failed to latch on to a through-ball that would have put him clear.
Umut Bulut then had another effort from the edge of the area that flew over the bar.
At the start of the second half nine-times European champions Real appeared content to sit on their lead but Eboue's goal transformed the atmosphere and it sparked a period of sustained pressure from the home team.
Sneijder dragged his shot well wide when he was unmarked eight metres out before the Dutch international struck Galatasaray's second goal.
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