We've only played 5 games against winning teams (as their records stand today). Those being 2 against NE-which most teams lose against, 2 against Jets and won one which isn't bad to be 1-1 against a team in your own division and the loss to the Ravens before the Bills started getting their act together. I would say that's not too bad, at least they are beating the teams they should beat.
Arguments about the opposition's records really make no sense in today's NFL. You have your elite teams, usually 2 or 3 of them, which are very difficult to beat. Then you have your teams that absolutely suck and this year there is really only one, the 49ers, and everyone else that can beat each other at any time. Any time you get a win in today's NFL, its a good win and a win against an elite team is a great win.