Based on driving fun and scenery, I'd base the game on the following courses.
Circuits:
Suzuka, Japan
Luguna Seca, United States
Daytona, United States
Estroli, Portugal
Donington, England
Spa, Belgium
Nurburging, Germany
Zandvoort, The Netherlands
Monza, Italy
La Mans, France
Suzuka and Spa are the demanding technical circuits that are full of surprises. Donington, Laguna and Zandvoort are more graceful, but can be just as tricky in wet weather. Nurburging, Le Mans and Monza have the history, with Monza having an old speedway type oval. Daytona has that capability, which is legendary, but it also has pretty good road course capabilities. Estroli, along with Zandvoort and Nurburing, is a course that's hard to drive because all you want to do is look at the scenery.
I'd also add five street courses:
Tokyo
Los Angeles
Rio de Janeiro
Paris
Sidney