Tom Brady is the G.O.A.T because of the following reasons: 5 Super Bowl wins, 7 Super Bowl Appearances, Greatest Super Bowl Comeback Ever, Most Playoff Wins, Most Total Wins regular and playoffs, #2 for Most Regular Season Wins and only needs 4 to take #1, #4 All-time Pass Yards and TDs and #3 Passer Rating. And he has done it without currently playing with even one Hall of Fame player.
I know there will be some who say if Manning could have done this playing for New England or will say Matt Cassel went 11-5 when Brady got hurt. Manning has an amazing career and is a Top 5 QB. Cassel may have won 11 games, but he didn't make the playoffs. But none of that matters. We base greatness on what you actually accomplished and Brady has accomplished more than any quarterback ever. We judge greatness on what someone actually did, not on what they might have done.
I don't like it, but I'm willing to admit the truth. As of Super Bowl 51 Brady is the G.O.A.T.