Sorry - I disagree.
Brady (6'4" 225lbs) would have been just as strong and heavy as many of the guys on the defensive line in 1950, and, in his younger years, he was faster (and bigger) than most linebackers in 1950.
The game has changed, in large measure, because the players have changed.
Go back and watch a video of the 1972 Miami Dolphin perfect season.
Three things will jump out at you:
They are all small - they are all slow - and they are all white (well, not all white, but close).
Physically, there is no way to compare 2015 with those earlier eras.
1972 Dolphins were slow, and small? You need to not look at slow motion photos on the highlights. They were plenty fast, and plenty strong.
At 6'4" 225 Brady is not particularly strong. Steve Spagnola showed everybody in the world how you beat Brady: pressure, pressure, pressure, because he cannot take a hit. If I were offered Rodgers, Roethlisberger or Brady, I would take them in that order. Brady has no ability whatsoever to escape or extend a play. Unless his line keeps him pristine, he's severely limited.
You are kidding nobody but yourself if you think Brady was ever faster than a premier linebacker. And again, if you offer me a 6'0" 225 linebacker delivering a forearm to the face -- which was perfectly legal before the proliferation of Brady-inspired sissy rules, and certainly so in 1950 -- Brady would go down like Linda Lovelace: ugly and often.
There's no question that the current crop of football players is bigger, faster, and stronger in their own positions. And there's no question sports technology is better than it was in previous years. Nevertheless, despite steroids and all the newest technology, there is no baseball player who has ever come close to doing what Babe Ruth did. And I believe Johnny Unitas, YA Tittle, or Otto Graham [just for example] would have no problem shining as elite quarterbacks in the modern NFL.
The problem with all these "he's the best ever" claims for Brady is that they're being made by people with very short memories. That is in the nature of sports hype, fan enthusiasm, and sports "journalism," which always has enormous biases for the latest players. But that doesn't make it so.