Thirty goals rained in around Europe with Real trouncing Galatasaray 6-1 in Istanbul, holders Bayern Munich winning 3-0 at home to CSKA Moscow and Manchester United putting four past Bayer Leverkusen at Old Trafford. (Agencies)
Paris St Germain fired a warning that they will be a real threat with a 4-1 victory away to Olympiakos Piraeus while Manchester City won 3-0 at Czech outsiders Viktoria Plzen.
Ronaldo's reign as the world's most expensive footballer ended this month when Real paid Tottenham Hotspur 100 million euros ($133.49 million) for Gareth Bale but he underlined his role as chief conductor of Los Blancos with a dazzling display.
Bale, who is still building up his match fitness after missing most of pre-season, had the honour of becoming the world's most costly substitute until he joined the party in the second half, playing a part in Ronaldo's second goal.
Midfielder Isco began Real's rout while their France forward Karim Benzema scored twice in a satisfying evening for Real's new coach Carlo Ancelotti who was treated to a feast of counter-attacking football by his expensively assembled side.
"Things couldn't have started better for us. Scoring six goals is really good and will give us a lot of confidence," Ronaldo, who performed a stunning silky dribble for his third goal in stoppage time, told reporters.
While Real, beginning their quest for a long-overdue 10th European crown, issued a powerful statement of intent, the strength of some of their rivals for the silverware would not have gone unnoticed by Ancelotti.
Less than four months after Arjen Robben's last-minute goal secured the trophy for Bayern Munich the Bundesliga giants registered the first goal of this season's group stage after only four minutes courtesy of David Alaba's powerful free kick.
Robben was on target again along with Mario Mandzukic as Bayern's new coach Pep Guardiola's saw his side ease to victory.
Guardiola, who twice conquered Europe during his glittering reign at Barcelona, said he was relieved to start another Champions League journey without any stumbles.
"I'm very satisfied with the performance. The first game after winning the Champions League is never easy. Everyone always thinks it is, but it's not," he said.
Ronaldo's former Manchester United team mate Wayne Rooney scored twice in the English champions' 4-2 victory over Bayer Leverkusen as the Old Trafford club began their first European venture without Alex Ferguson at the helm since 1985.
Ferguson, who twice steered United to Champions League success, watched as Rooney's double and goals from Robin Van Persie and Antonio Valencia gave new boss David Moyes a pleasing, if sometimes anxious, first taste of the group stage.
"I said several months ago Wayne Rooney could join the real greats with his goalscoring. He could have got a hat-trick tonight," Moyes said of the England striker whose double took him to 200 goals for United.
"Robin van Persie's goal was also great. If we can get those two scoring, they can be formidable for us," he said.
Thirty goals rained in around Europe with Real trouncing Galatasaray 6-1 in Istanbul, holders Bayern Munich winning 3-0 at home to CSKA Moscow and Manchester United putting four past Bayer Leverkusen at Old Trafford.