I dont see GM out of the #1 spot anytime soon. GM and VW have placed bets early in China and I think that will reward both companies in the future. That being said, GM does need to change some things here in North America in order not to loose more market share to Toyota.

#1 End the confusing brand strategy (kill Pontiac, Buick, Saab, Hummer). You only need entry, mainstream, luxury and commercial trucks.
#2 Hire a decent designer. Harley Earl, Bill Mitchell and the like put GM on top. Todays product is bland or ugly.
#3 Get serious about appealing small cars. They used to be good at it a very long time ago (1961-1963 Skylark, for example). If you dont capture young, first-time buyers, you can loose a whole generation of customers.

Jim