"He has evolved and I am sure he will evolve even more," former Brazil and Barcelona striker Ronaldo told reporters in Rio de Janeiro on Thursday.
"If he keeps getting better he will be the best player in the world."
"I am sure he'll be coming to Brazil an even better player," he added.
Ronaldo, whose sports marketing company has Neymar on its books, has good reason to talk up the 21-year-old and told the former Santos player that he needed to go to Europe to fulfil his potential.
While the young playmaker has been criticised for diving, he has shown in his first few months in Spain that he can shine alongside the best in the world like Barca team mate Lionel Messi and Real Madrid and Portugal forward Cristiano Ronaldo.
"I am delighted with Neymar's start, he's playing well and scoring and creating goals," said the Brazilian Ronaldo who also had spells with Real, Inter Milan and AC Milan.
"He has Messi alongside him, who is out of this world. In every game he is brilliant and scores two or three goals," he added of the Argentine forward.
Ronaldo is on the World Cup organising committee but is now spending most of his time in London where he is studying business and marketing.