Ronaldo, who now has 51 career trebles, was also instrumental in helping Real clinch a third consecutive Champions League trophy last month.
Although Hierro hailed Ronaldo's skills, the former Blancos captain insisted that he would not trade the former Manchester United man for any player in the Spain squad.
"When you are playing a player like Ronaldo these things can happen," Hierro told BBC Sport. "When you have a player like Ronaldo, it is extremely fortunate for whichever team has him.
"I have a really good relationship with Ronaldo, but I certainly would not change him for any of the players in my squad."
Portugal and Spain sit second and third in Group B, with Iran top of the standings after the first round of games following their 1-0 win over Morocco earlier on Friday.