The Barcelona defender believes the Portugal international's drive and determination is why he is considered one of the best players in the world.
Ahead of their Clasico encounter next Saturday, Pique admits it is hard not to like Ronaldo for his hard work and endeavour.
He is quoted by Marca as saying: “[Cristiano Ronaldo] has not changed; he is a player that I have always admired because he is a hard worker that always wants more and more.
“He is a real machine and very ambitious. He never ever stops trying to improve.
“Some say he is the best but he still wants to get better, and for that reason I admire him.”
Pique also commented on the longstanding rivalry between Barca and los Blancos, claiming they have surpassed Madrid since the turn of the century, with the help of their youth academy which has produced most of their first-team stars.
“Barcelona have always been behind Real Madrid, but in the last 10 or 15 years we have turned the situation around," he continued.
“We are talking about a Real Madrid that has dominated football for 90 years and that has always been ahead of us.
“We have brought through a great crop of youngsters at the club and this has helped us to compete.
“Real Madrid go one year without winning a title and they spend €160 million on three players: [Asier] Illarramendi, Isco and [Gareth] Bale. Barcelona can sign Neymar for €60 or €70 million but not three players.
“The day we do not have La Masia, things won’t be the same.”