All games are almost equally important, with divisional games and conference games just slightly more so. And yes, non-conference games are also very important.
It is a sport with only 16 games. Nobody can claim one game isn't important unless you have already clinched a 1st round bye in the playoffs or can't possibly improve your playoff standing.
I don't get it. The Bills DID beat Brady a few times. Or are you saying specifically McDermott's Bills?