Ramos is now 34 and in new contract talks with Real.
"For me, he is the best defender in the world," Van der Vaart told Stats Perform News.
"When I was at Real Madrid, he was 21 or 22 and bursting with energy. He wanted to be everywhere. Free kicks, corner kicks, everywhere. Now it is different, he has so much focus now. A focus on winning and he uses all his talents for that purpose.
"He's aware of his skills, strength and conditioning and that helped him being so important for his team in winning already so many titles. His body is unbelievable, he is a machine. When I was watching a game the other day, I thought, 'how old is he? 34?' I believe he can still be playing for another six years, I've so much respect for him."