Car design has to evolve to stay relevant in the market place simply because of what people want to buy. But in some cases the original instantly becomes a classic recognizable shape and nothing after that compares favorably. Sports Cars like Mustangs, Cameros, Challengers, Z's, etc, etc are good examples and have all gone through some pretty rough abominations. Mustang and Camero stand out the most for me for some reason.
Like @Captain Obvious, I want to say I see the original lines in the later Z models, but really I don't. Kind of like knowing some brothers and/or sisters. You know they're related but they don't look the same (excluding twins of course).
I think American manufacturers can play the nostalga/retro design with some success, but I don't that is something the Japanese manufacturers would do, in my opinion.