Buffon, 41, left in the summer after 17 years with the Bianconeri and joined Paris Saint-Germain, while Ronaldo arrived from Real Madrid.
Speaking ahead of Juve's visit to Atletico Madrid in the Champions League round-of-16 first leg, Chiellini has said swapping the goalkeeper for the forward has worked as a like-for-like transfer terms of the two players' influence off the pitch.
"The arrival of Cristiano is important because it filled the void left by Buffon in terms of his personality or as an example to follow in the dressing room," Chiellini, 34, told Marca.
"Because Ronaldo, aside from what he does on the pitch -- and only a crazy person would question him because he scores goals and creates them -- has been important for us because he has been an example on how to better ourselves.
"After many years dominating in Italy, we could assume we'd reached our maximum, but thanks to Cristiano, we are doing even more than we thought we could -- searching for new limits.
"We have reached two Champions League finals but, in order to carry on growing, we needed the best. He has helped us with his work ethic because whoever is near him feels admiration and we are always trying to 'rob something' from him because he is an example."
Juventus and Atletico have been the losing finalists in four of the past five editions of the Champions League and meet on Wednesday in the round-of-16 first leg.