The 26-year-old admits he admires his former Manchester United teammate's ambition and claims Barcelona is "a poor club" when compared to Real Madrid's spending policy.
The Real Madrid forward has finished runner-up to the Argentina international in the Ballon d'Or for the previous two seasons as the attacking duo continue to vie for the title of the world's best player.
Pique, who played with Ronaldo briefly at Manchester United, feels the 28-year-old is motivated by the constant comparisons with Messi and has praised the Portugal captain for his ambition.
"Cristiano Ronaldo has not changed since we were both at Manchester United. He remains the same," he told So Foot. "He is a player I've always admired because he is a hard worker who always wants more and more. He is really ambitious. For me, he is in the top two or three in the world and still wants progress.
"I believe that his rivalry with [Lionel] Messi has helped Cristiano Ronaldo to always go further."
Pique went on to highlight the differences in spending between Barcelona and Madrid over recent seasons, suggesting the Blaugrana has performed admirably to keep pace with its bitter rivals given the comparative outlay in the transfer market.
"We are a poor club, but we are the rival of the world's richest club," Pique continued. "If you look at the starting 11 of Madrid and see all the money they have spent to build it up, then you see there is no possible way for Barcelona to compare. They went a year without winning a major title and invested 160 million Euros on three players, [Asier] Illaramendi, Isco and [Gareth] Bale. We can pay 60 million Euros or 70 million Euros for Neymar, but that's it."
Pique once more suggested the players are "slaves" to the style of football ingrained in them from youth level upwards in Catalunya, adding that the more "individualistic" players of los Blancos are more likely to adapt to other sides.
"I think we are slaves to our style, in the sense that a player made in La Masia will have problems on a team that does not have the same identity and which, for example, does not like to have the ball. In comparison, a player trained in Madrid is more individualistic, which is not bad because it means you can fit anywhere.
"If you look at the big leagues you will see that there is always more former Real players like [Esteban] Granero, [Alvaro] Negredo, [Ronerto] Soldado and [Juan] Mata."