The 39-year-old, who also played for Barcelona and Inter Milan, said his compatriot reminded him of himself.
"I like Neymar a lot. He is a bit like me," he told Calciomercato (via Goal.com). "He had some difficulties in getting used to his new environment at first, but I knew that he was going to succeed."
Ronaldo anticipates Neymar to be the successor to five-time Ballon d'Or winner Lionel Messi at Camp Nou.
"Can he be Messi's heir? Yes, he has everything he needs to become as strong as him.