I stumbled upon this..months after it was published, but found it amazingly accurate. I've owned about 25 cars, and driven most of the others on this list and I agree with it and the ranking order.

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"Fun to drive" is a subjective measure—an elusive quality that can mean different things to different people. From our experience, a car can have a very powerful engine and accelerate quickly, but without handling agility, it’s not much fun. For us, fun is a combination of factors such as handling response, sound, and the nature of the power delivery that lead to grin-inducing satisfaction. Here are the top fun-to-drive models that we’ve recently tested in order of ranking:

* Porsche 911 Carrera S
* Porsche Boxster
* Honda S2000
* Mazda MX-5 Miata
* Chevrolet Corvette Z06
* Mercedes-Benz SLK350
* Infiniti G35
* Mazda RX-8
* Volkswagen GTI
* BMW 328i
* MazdaSpeed3
* Subaru Legacy GT
* Mini Cooper S

Source:
Most fun cars to drive: Consumer Reports Cars Blog