Ronaldo won the Ballon d'Or twice and the FIFA World Cup in 1994 and 2002 but saw his career curtail due to serious knee injuries.
However, during his prime, he represented both Real Madrid and FC Barcelona, with whom he produced some of the greatest individual displays world football has ever seen.
And Carlos suggests that during that era, it was harder to find the net as defenders were allowed to be more robust as the laws of the game have been tweaked within the modern game.
"Ronaldo was the best. Neither Messi, nor Cristiano, nor Neymar," he told Goal when asked who's the greatest player of all-time.
"There will never be another 'Fenomeno'. I think that in our generation it was more difficult to score goals. It was more physical then and the attackers were less protected, yet Ronaldo could do of everything."
Ronaldo's best-ever season at club level was with his solitary season at Barcelona in the 1996/97 campaign, when he netted 47 goals in 49 games across all competitions to win the Golden Ball.