The fact that Brady is the greatest ever doesn't mean Manning wasn't a great QB. He obviously belongs in the pantheon with Montana, Unitas, Starr, Baugh, and Graham.
The parochial insecurity of Bostonians isn't in their insistence that Brady is the GOAT. He is. It's their insistence that everybody else must suck. They were the same way about Orr.
To sum up: Brady is the greatest and Boston sucks even harder for it, perhaps because of their niggling cognition that the Patriots will always be considered an also-ran franchise. Pittsburgh, Dallas, Green Bay, and even the Giants are great franchises, The Patriots are temporarily wealthy bums to be tossed right back in the alley the day Brady retires. My god, Oakland is a more important franchise than New England and they've sucked for 20 years and are about to be kicked out of their own city.
Boston is a city of losers having one of the greatest streaks in sports history and they awake every day to find than every win brings them no closer to being a respected American city, let alone a world one. That is what is at the bottom of the habitual sand in the swimsuit crack of the Bostonian.