Pontiac Fiero
While most drivers wouldn’t consider the Fiero one of the best GM cars ever built, it was in many ways. The Fiero was one of the first mid-engined sports cars ever sold on the domestic market. The Fiero also had an advanced suspension that made it handle better than almost anything else on the road (via Hot Cars).
Although early Fiero models were prone to engine fires and a lot of issues overall, the last models were nearly perfect. The modern design which came at the end of the cars life was very attractive and these are the Fiero models that collectors seek the most.