Valuev is certainly much better than any other fighter of his size who has fought at world level, but at the same time he is no world beater. I have never bought into the argument that smaller ATGs would not be able to reach his chin. In the few cases we have of similar height disparities, they seem to manage.
But you can visually see that Hatton who is the same height as Langford can't reach his face. You've listed a random none boxer who was giant, Valuev for his size has decent skills maybe superior to Willard, he's not simply an OAF Fulton wasn't great either and you seem to consider that a good win for Fulton. Fighting a 6'5 fighter was undoubtedly an issue for Langford Qawi is similar to Langford, maybe 5'9 Tua is, contrary to what many believe Tua had very good technical skills but had problems giving up height so often Langford generally got beat by the good big men of his time, ie Jack Johnson and Wills. He beat world level opponents so he is a world beater No there isn't 'similar height disparities' Haye and Holyfield are 8/9inches taller than Langford, massive difference