Neymar, 22, has endured a difficult first season in La Liga, but has managed to score nine times in 25 appearances for Barcelona.
Ronaldo, widely considered one of the world's best along with Lionel Messi, said Neymar had all the attributes to be regarded as number one.
"I think Neymar is a great player. I think he's shown over recent seasons that he's one of the players of the future and has every possibility to be a major talent," Ronaldo told SporTV .
"He didn't adapt that well to Barcelona, he had some problems at the start, but I don't have any doubt that he has the potential to be one of the best players in the world, or even the best."
Ronaldo and Neymar are both expected to play a major part for Portugal and Brazil respectively at the FIFA World Cup.
Portugal take on Germany, Ghana and the United States in a tricky Group G, which Ronaldo believes is the toughest at the tournament.
"We're not favourites, but we'll try to enjoy ourselves," Ronaldo said.
"We know we've got a tough group stage, in my opinion the toughest in the World Cup, but we'll take it step by step.
"We've got an important game against Germany in the first match and then Ghana and the US to get through to the group stage. After that, we'll see."
