If people were asked to guess what the best-selling sports car in the world is, there’s a good chance that the answers would have as much variety to them as the number of colors in a Skittles pack. The Mazda MX-5 is a good answer. The same goes for the Porsche 911, and at least for new models, the BMW 4 Series. All three models have proven to be popular among buyers all over the world, but none of them can lay claim to being the best-selling sports car in the world. That title now belongs to a certain muscle car from Dearborn, the Ford Mustang.