Ronaldo left Real Madrid to join Juventus in the summer, having scored 450 goals over nine seasons with the capital giants.
Atletico finished above Los Blancos in La Liga last season, and Simeone has insisted that his side "have approached Real Madrid's level" due to Ronaldo's summer exit.
"From the results we aren't worse than Madrid or Barca, from the individual characteristics of our players, yes. Without Cristiano we have approached Real Madrid's level, for sure," Simeone told El Partidazo de COPE.
Atletico have collected four points from their three La Liga matches this season, while Real Madrid have maximum points from their three fixtures.