If anyone else had made this argument, I probably wouldn't have an issue with it. But, coming from Montana, it sounds self-serving, which, no doubt it is. Not to mention, a little petulant. Otherwise, I would have said it sounds a lot like things I have stated in the past. The game of Professional Football has evolved considerably over the last 75 or whatever years.
I'm older than a lot of you and I've often gotten into the Sammy Baugh/Otto Graham, pre-SB era discussion out here in the past.
There are the clear SB era greats in Brady, Montana and Staubach; then, you can further subdivide the SB era into pre-cap and post-cap, so it's Montana and Staubach pre-cap and Brady by himself post-cap. I don't include Young in the pre-cap discussion because then you have to bring people like P. Manning into the post-cap discussion.
Brady, Montana and Staubach defined their eras. Young and P. Manning are in the discussion in comparison/reference to others; in the case of Young, compared to Montana/Staubach and, in the case of P. Manning, compared to Brady.
Starr and Unitas are sort of in a no-man's-land between before and after 1966, or the beginning of the SB era, but they both defined that"era," whatever it might be called. But, it's probably unfair to leave them out of the discussion.
So, for my money, with seven AFC Championships, five Lombardis, four SB MVP's, two League MVP's and virtually every Regular Season and Playoff statistical record, Tom Brady has the strongest argument for Greatest of All Time.
But, if purists (i.e., specifically not a contender like Montana) want to argue that there is a small group of QB's for whom an argument can be made that they are the Greatest of All Time and that that group includes Baugh, Brady, Graham, Montana, Starr and Staubach...well, that's fine by me.
It's no disrespect to Brady to put him in the discussion with the other five. But no one will ever convince me, personally, that he isn't the Greatest of All Time.