Hummer sold well, but with rising gas prices, becoming the poster child of waste, etc didn't exactly spell a good future for Hummer. GM tried to sell Hummer to a Chinese company, but China didn't want the baggage that came with Hummer and blocked the sale.
Saab was dying no matter what. All GM's purchase did was delay the inevitable. But GM never got Saab and what created their loyal following so they were able to revitalize it. The Saab 9-3 was based on GM's Epsilon platform( Malibu, Pontiac G6, my Saturn Aura, Opel Vectra), the 9-7x was on the GMT-360 platform( Trailblazer, Envoy), the 9-4x was going to be on Theta-Epsilon( current Cadillac SRX), and the new 9-5 was on GM's Epsilon II platform.
You're thinking of the Chevy Aveo which was based off a Daewoo car.
Not going there with the flip up headlights debate. I bet you think the Corvette got double killed when they ditched the round taillights..... And you'll probably think it will get triple killed when/if it goes mid-engine for the C8. The flip up headlights were cool only when they were down, sucked when they were up.