I am never counting GTs to compare riders for listing them as the best. Different years, different competition. In general during the times of LA and most of the years of MI the competition was not that strong for example.
I prefer to remember all GT cyclists I have seen in my life and balance my "gut feelings" and some objectivity. I would say that right now Contador seems to me almost there with Lemond and Hinault, equal to Indurain and Armstrong, way over Fignon, Pantani, Roche, Delgado or Ulrich.
As for Mercks, Anquetil, Ocana, etc... I was not there, I can´t say
But I must say given Contador´s amazing racing style, character and age he could be soon the best I have seen. If he wins Tour and Vuelta this year he will be, no doubt. To me.