I think we're just more capable of looking at these things with relativity. For example: Mark Sanchez. Went to back-to-back AFC championships. Does that make him a successful quarterback per se? Or did he just have a great team around him?
For example: Carson Palmer. He was an absolute disaster with the raiders. But he was pretty damn good with the Cardinals.

Stafford for example: is it reasonable that a quarterback can have Stafford's numbers and only go to the playoffs three years out of 10? Or is it just that the organization he was with was that bad? I think we've all come to the conclusion that wins are not exclusively a QB stat. Sure they play the most part but you can win with an above average one and you can lose with a great one.