Well, look at players like Neo, Taj, Chu and Dire. All of them play low tier characters and are well known for their skill at those characters.
Neo's Roy has beaten Husband's Marth, and he competed with Ken. Even though he lost that match, he put up a good fight. His Roy has defeated several players he "shouldn't" have been able to beat, many of which can be found on youtube. Watch this guy play.
Taj 0-death's Fox and Falco all the time with his Mewtwo. He can beat Forward's Falco, and Forward is respected and looked up to by many, myself included. While he does do best against fastfallers, it's not just them he beats ether. I've seen matches where he tears apart even floaty chars, including Peach and Samus. You have not experienced life to the fullest if you have never seen Taj's Mewtwo.
Chu mains the IC's, but those guys aren't who I'm talking about. I'm refering to his Pichu. Chu has beaten good players with his Pichu, and once again, I advise you to watch this guy play. It's pretty amazing.
And of course, Dire's famous G&W. He lost to M2K's Fox, but the match was so close, it was scary. Watch this guy play too.
So...my theory is that no, there are no bad characters. People just don't have the patience to learn the ones that are less used. I mean, how many people can do what Taj's Mewtwo can? Not many. But if more people acualy took the time to main Mewtwo, maybe they could.