I was a GM technician for 14 years both in Australia and Canada and am now a VW technician. The build quality of VW is something GM will never come close to matching.
On any car forum like this one you're always going to hear about the people who have problems because the people with problems are coming here to see if anyone else is in the same boat. It's very rare for someone to just start a new thread saying that their car is running perfectly and has never had a problem because they're not asking for help and they're not giving much information to other users.
I could rattle off several problems with GM vehicles. I did start writing a list but it got way too long for anyone to bother reading.
As for the Commodores with the Chev badges I'll never understand it. Just because it has a Chevrolet designed engine in it doesn't make it a Chev. You never saw people with the 3.8L V6 with Buick badges on their cars. Besides that, Chevrolet is the poverty brand for GM. Every other GM brand is considered higher. It's why Holdens were badged as Pontiacs (GTO and G8) because even Commodores are better than Chevrolets. Don't get me wrong, Pontiacs were crap too before they were dropped by GM.