The Portuguese marked winning a fifth Ballon d'Or crown of his career earlier this month by playing a key part in Los Blancos' Club World Cup success.
Ronaldo scored the winner in the final against Gremio on Saturday to make it 16 goals in 21 games this term, and Ramos believes that the 32-year-old is deserving of his accolade as the world's best player.
"Our number seven is a striker like we have never seen before," he told Telefoot. "He is already a legend and will be recognised as one of the best players in the history of football. Cristiano Ronaldo has a very important role in the team and everyone respects it."
Reports emerged last month of a rift between Ramos and Ronaldo in the Bernabeu dressing room, which the Spanish centre-back has since played down.