I dunno if bankruptcy would help or not. But what they really need for the long run is simple: Better design. They're getting their butts munched by Ford, ~and~ Chrysler fer cryin' out loud.
I don't even really like the new Chrysler style all that much, but it definitely shows an outta-da-box style shift. It will work for them. Ford has completely hit one outta the park with the 05 Mustang. They will sell a buttload of those.
GM needs to make some fun cars, and then people will buy them. It is precisely that simple.