Portuguese forward insists Pep Guardiola's side have "a lot of influence, both on and off the pitch" following Madrid's Champions League defeat at the Bernabeu
Defensive midfielder Pepe was handed a straight red card in the second half for a challenge on Dani Alves, subsequently, Madrid coach Jose Mourinho was sent to the stands for his gestures towards referee Wolfgang Stark.
Lionel Messi's brace after the interval, his second goal, a superb individual effort, secured the first-leg advantage for Pep Guardiola's side but Ronaldo has insisted Barcelona have received the benefit of referee decisions in previous European campaigns.
"It's always the same with them [Barcelona]. This is the fourth consecutive season that something like this happens. Mourinho is right, just look at what happened with Arsenal, Chelsea and Inter," Ronaldo told Sky Sport.
"They [Barcelona] are a fantastic team, but they also have a lot of influence, both on and off the pitch."
Ronaldo conceded his side's display was poor but admitted the sending off changed the game and as a result, the tie is tipped in Barcelona's favour.
"It's true that we didn't play well. However, it was still scoreless when it was 11 versus 11 and everything was still possible. We could have scored a goal. It will now be very difficult for us though."