GM is in trouble because there is a perception in "the market" that better products are made by other companies.
The big problem, especially for bigger companies, is: the definition of "better" is a moving target. "Better" used to mean "Faster", hence the big engine craze of the 60's/early 70's. Then, with a fuel crisis, it meant more efficient...hence the Japanese small car proliferation. Then as fuel became cheaper (figuring the cost of inflation), "better" became "Bigger"...hence the SUV Urban Assault vehicle popularity. Safety was also associated with "bigger", helping the perception of bigger being better. However, with single vehicle deathrates reportedly higher in SUV's (due to one factor....rollover) than almost any other non-motorcycle vehicle, combined with fuel prices escalating, "better" may require higher fuel efficiency. And so "better" continues to change. If the economy is perceived to be bad enough, Value becomes more important, conversely, when it's all roses, Appearance or Performance becomes more important.
Whether these statements are exactly correct doesn't matter, it's the concept that's valid.
Companies that can hit the "better" moving target the quickest are usually the companies that thrive. Maybe GM will be quicker in the future. Maybe not. Success depends upon hitting the target quicker than the "others".