The Barcelona defender, who played with the Portuguese attacker at Manchester United, believes the comparisons with Lionel Messi spur both players on to become even better
Before moving to Spain as Clasico rivals, the two players were colleagues at Manchester United and the Camp Nou centre-back admits seeing the Portuguese star at close quarters has given him a positive opinion.
Pique told Esport3: "As a team-mate, Cristiano Ronaldo is a perfect ‘10’.
“I admire him professionally because he sets an example to follow both as a player and as a person."
The long-running debate over who is the world’s best player shows no sign of ending as Ballon d’Or voting continues and Pique believes the rivalry between Ronaldo and his current team-mate Lionel Messi spurs both of them on to greater heights.
The 26-year-old continued: "Cristiano's good turn of form will make Messi come back with even greater enthusiasm.
“The competition between Messi and Cristiano has made both of them better."
Despite sitting top of La Liga, Barcelona have come in for criticism at stages this season and the Spain international concluded by admitting Gerardo Martino’s side can still improve.
"We could play better - the debate over our style is a wide-ranging one,” said Pique.
"But the team that won six titles was not just the best Barca team; it was the best in the history of football."