I think the tell tale sign of any specific models success was/is due to a less aggressive design. Looking at the beginning of the Mustang sales, the car had a wide appeal due to the styling being attractive to a broad spectrum of people. Ford did a refresh for the 1967 model and sales dropped in part to competition from Chevrolet, a more aggressive appearance for the Mustang and probably a topping out of the market segment.
Looking at the sales of the Mustang II

it did well because it was cheap and conveyed a presence that it was non-threatening. Lot's of people look for cars like this so as not to attract unwanted attention to themselves.
Ford softened up their appearance for the new Mustang and sales have responded accordingly. It looks like GM has followed suit with the Camaro, yet they went the other way with the Corvette. We'll have to wait and see if the strategy for the new Camaro will have it's desired result for Chevrolet and it's parent company - GM. IMO, the interior and performance options will help year-to-year sales growth for the Camaro, but I'm not sure about it maintaining its sales lead over the competition.
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2015 CRT 1SS/1LE RS/Recaro's/NPP/Nav/Rear vision pkg./BA speaker upgrade. Stage 3 BMR cam, ARH 1 7/8 headers, CAI,
BMR 1.25 drop springs, JPSS Billet Bushings, Peddars Cradle Bushings...460 whp...so far....SOLD, but not forgotten!
