What's the deal with you all and extremely long tracks? I always wondered that.
Road Atlanta is in Forza Motorsport, and I've raced it in "Le Mans 24 Hours" on the PS2, then "Sports Car GT" on the PC. The track is so balanced. The turns consist of semi-technical corners, nice straights, and the ever popular Esses. The track is a test of your suspension and top speed. You have one tough American track (Sears Point), why not another? If GT5 will have 20 to a track, there's another American track that can fit those 20- Lime Rock Park. Lime Rock Park is in Connecticut and is my idea of a short track. The configuration almost seems like an oval, just a pretty simple-looking track.
Now on to Japan. I raced TI Circuit Aida in "Jarrett and LaBonte Stock Car Racing" (good game, bad name) and Sugo in the same game. TI Circuit Aida is a somewhat long, technical circuit. It is a sweet course to race on, and will greatly suit the JGTC race cars, as it's been a JGTC/Super GT venue. I believe Sugo also is still a JGTC venue. Sugo is a bit different and not really challenging.
I'm not trying to come up with a world of tracks, but these are suggestions I have. For now, I think we can all agree on Bathurst. Why Bathurst? It's the toughest and most prestigious course in Australia. The course really puts you to the test. There are some easy-flowing straights, but most of the rest of the track is technical turns ready to beat up your car's suspension and wear out your brakes. And, oh yeah, it's fun too! (^_^)