Only sales to government parasites prop these crappy car companies up. No one buys these cars. Ever see one? They are total history.
Most of the new GM vehicles I see on the road (with temporary tags) are Chevy Camaros. That's an "enthusiast" car with a fan base that is arguably broader than that of the Corvette - and they had to wait a number of years for GM to put it back in production. So I can understand why that model is selling.
Other than that, I don't see much rolling off of the dealer lots. Fleet sales are definitely GM's bread and butter these days - they brought the RWD Holden (GM Australia) chassis (formerly seen as the Pontiac G8) back as a Chevy Caprice for the law-enforcement market. The departure of Ford's Crown Victoria sedan opened that door of opportunity for them.
They can't survive without government fleet sales. Even that may not save GM; I'm seeing more Dodges than Chevys with U.S. Government plates these days.