Mahomes is 29, 30 in mid September.
Brady had a 5000+ yard season after the age of 40.
Right now Mahomes isn't close to Brady and he probably isn't number 2 either.
I believe he will end up #2 and the gap between him and Brady will shrink, but by the end of his career, he'll still be #2. When Mahomes retires my bet is on Brady still having more SB wins, more SB appearances, more conference championships, more divisional titles, more passing yards, and more passing touchdowns. AND I don't believe that Mahomes' peak level of play to this point surpasses Brady's (or Rodgers' or Manning's or possibly Dan Marino's).
I believe you are wrong. I recently saw an article by Bill James a baseball statistician who was working with Pro Football Reference on just this question. He came up with Peak value and Career value. His bottom-line conclusion was..............
Career Value..........Brady is the GOAT.
Peak Value..........Through his first seven seasons, Mahomes is the best QB in pro football history.
Of course, Mahomes Career Peak Value, TBD.
You say you don't believe Mahomes peak level of play surpasses Brady, Rodgers or Manning, sorry but it does.
Quarterbacks through their first seven seasons since 1950 with at least 1,000 passing attempts. Mahomes in the regular season is...........
First in completions.
First in passing attempts.
Sixth in completion pct.
First in passing yds.
Second in passer rating.
First in Adjusted Net Yards.
First in Succes Rate.
His value in the playoffs is even better.