Charlton, now a United director, rates the Dutchman ahead of Peter Schmeichel.
"He is perhaps the best we've ever had at United," Charlton told De Telegraaf.
"With our defenders, Edwin influenced their qualities in a positive way. Look, we have talented stars like Ryan Giggs and Paul Scholes in the ranks. But Edwin led them, he provoked them to get better. Without any discussion."