As a matter of FACT, Brady has made Belichick...
Belichick without Brady:
7 seasons, 51-62 regular season record, 0 division titles, 1 postseason (1-1 record), 0 Super Bowl championships
Belichick with Brady:
10 seasons, 124-35 regular season record, 9 division titles, 9 postseasons (16-6 record), 6 AFCCG appearances, 5 Super Bowl appearances, 3 Super Bowl championships
The disparity is plainly obvious.
Taking a closer look, Belichick began his tenure in New England with a 5-13 record. After Brady became the starting QB, the team went on a 14-3 run that culminated with their first Super Bowl championship. In total of course they would go on to win 3 of 4 Super Bowls. It's not just a coincidence that Belichick became a winner immediately after Brady became his starting QB.