The former Brazil international spent a season at Camp Nou but expressed his affection for Los Blancos following his five-year spell at the Santiago Bernabeu
The former Brazil international established himself as the most exciting young forwards in the game during a wonderful season with the Blaugrana between 1996 and 1997 but later spent five years plying his trade with the Catalans' great rivals Real.
However, while he freely confessed that his loyalties lie with Los Blancos, Ronaldo finds it difficult to rank Jose Mourinho's men above Pep Guardiola's Barca.
"I’m a Merengue and I really like the way Madrid are playing, but you can’t ignore Barcelona, who have a fantastic team," the legendary striker told Fifa.com.
"They may not be the most spectacular, but they make everything look so simple. Every single player in every area of the side knows what they have to do at any given time.
"Then you’ve got their ability to keep hold of the ball and the way they patiently work their way towards the opposition goal.
"The great job that Guardiola has done shines through; they're one of the best teams I’ve seen in my 35 years on the planet.
"It hurts to say that, since I’m a Madridista, but I still think we can pip them to some titles this year."
Indeed, Madrid are currently four points clear of Barca at the top of La Liga, ahead of this weekend's Clasico at Camp Nou, and Ronaldo is desperately hoping that Los Blancos can reclaim the title in light of his enduring love of the club.
"I look back at my time at Real Madrid with a lot of affection," the World Cup winner admitted. "I think it was the best period of my career.
"I also really enjoyed it at Inter, as I fell in love with the team and the city of Milan. But wherever I played I made a lot of friends and had a great time."
Madrid face Bayern Munich in the semi-finals of the Champions League, with the first leg scheduled to take place at the Allianz Arena on Tuesday at 20.45CET.