Ronaldo has enjoyed great success over the past 10 years, both individually and with the likes of Real Madrid, Portugal and now Juventus.
The five-time Ballon d'Or turned 35 in February but continues to play at high level, after netting 25 goals in 32 appearances this season.
"Ronaldo is the best of his generation and a huge example for young players," De Ligt told Tuttosport.
"I always try to improve the way I play by watching him because even in training he has a crazy intensity and you wonder if he really is 35 years old.
"We really have a good team, a lot of good guys. The most fun are the South Americans. Beside Ronaldo, I was impressed by Paulo Dybala and Rodrigo Bentancur: both players with an amazing technique.
"Rodrigo in particular is underestimated, he will have a great future ahead of him."