Real were cruising in their first European outing since their 250 million euros spending spree when Ronaldo, Raul and Gonzalo Higuain scored in an 18-minute spell before half-time in the Group C game.
The Swiss champions hit back with two goals in a minute during the second half but two late goals, from Ronaldo and Guti, secured the win.
"We had a few defensive problems and we mustn't keep losing concentration," said Real coach Manuel Pellegrini.
"There are always things to improve but I'm happy we scored five goals."
Raul slid in Higuain's angled shot seven minutes later to take his Champions League tally to 65 goals and Higuain, repeatedly overlooked by Argentina coach Diego Maradona, himself fired the third in first-half stoppage time.
Ronaldo ended their comeback with a long-range effort in the 89th minute which slipped through goalkeeper Johnny Leoni's hands.
With this year's final being played in their own Bernabeu stadium, a 10th European title is seen as almost an obligation for Real, especially after investing in Kaka and Ronaldo.
