Well it doesn't really validate your point, does it? Unless you think people beleive DDG is the best in the world because he's faultless. A keeper is bound to make more visible faults than a defender, that's just part and parcel of the job role, and so makes your comparison somewhat of a strawman. Instead compare Ramos to other centrebacks. Would you say Ramos makes comparatively similar mistakes than someone like prime Chiellini or Bonucci?
I think it's also important at this point for me to state that I rate Ramos very highly.
He is the best for his two transcendental goals, in 2 champions league finals, as well as for other qualities, from leadership to ability to excel in important games. He has not failed in many important matches, and if he did many times he was able to amend it with a goal.
Today the best full back is the one who knows how to attack, increasing the density of the defense in the game play.
In the case of defenses, the ability to play the ball with quality is important, and in that case, he is also one of the best.
The level of protection and defensive intensity of each team must also be taken into account.
One thing is Cannavaro in the World Cup with Italy and then finding himself in the Bernabeu very alone.
Considering two choices: technical defense which contributes in attack versus "classic" CB that exceeds in defense I think that in the balance, I would choose a defense type Ramos, but even considering the other election I do not see nowadays anyone else with a superior level (vidic type, Pujol , Maldini, Nesta,etc)