Rod99-
I think you're measuring the ability of federer's BH incorrectly. In my opinion, the only way to truly measure the ability of a certain shot is to see how the player uses it in the rest of his game. this is why Fed's BH is sooooooooo good. All those names you mentioned are probably more likely to hit a winner off the BH than Federer is (on an average day). But none of them use the BH to set up the point like Fed does. If Fed's playing someone who doesn't like the net, he teases them with a slice BH, forces them to either take the net (which they don't want to do) or hit a weak shot that he can put away. He's done this countless times against Roddick, Davydinko, Hewitt, and many more. Sometimes he flattens out his BH, sometimes he rolls the ball at an incredible angle. although he doesn't always hit winners off that wing, it is more than effective than many other BH's and allows him to put himself in a position to win the point.
Agassi's serve is very similar. I've always thought that agassi's serve (especially toward the end of his career) was one of his strengths, and one of the best serves out there. he didn't step up to the line and hit aces, but he placed it/spun it so he could start off the point at an advantage. Federer's backhand is the same way.
If we were judging Fed's backhand purely on how many winners he can hit, then some of those you mentioned might be ahead of him, though in my opinion not many. but tennis isn't about hitting winners and you're allowed to hit more than just BH's, that's why your idea is completely ridiculous and has no truth to it.
Finally, you're judging fed's BH purely on his "bad" days. You find the best backhand Fed's ever hit, and I guarentee you it's a million times better than any of those clowns' you mentioned before.