Though GT4 graphics are great, the quality of graphics in GT3 were just fine. So was the movement of the cars in GT3. The handling of the cars were a little off; GT4 is better at that. But, overall, PD should have increased the performance of the AI more than what they did. (Which was zero, BTW.)
Yes, they come here to read what we say. I bet they take our ideas seriously too, mentioning them at meetings. It would be stupid not to. It would also be stupid to mention every idea here... he-he.
For GT5, the first priority should be improved AI. Then, features like more cars on the track. Then, better vehicle movement. GT4 cars moved too twitchy and not smooth, like in GT3. I'm sure handling can be improved a bit, which should be next. Next, car sounds. Better engine and exhaust notes. More creaks and suspension noise. Next, image improvement and more details of track background and objects, such as trees, clouds, people, grass, leaves, tire smoke, dust, planes, blimps, etc. Note; the track itself, and the track buildings in GT4, looked good enough. Next, car image quality and details, specifically reflection off of the cars, including working, user-activated head lights and horn, glow-in-the-dark racing decals for race cars, LED race position lights, etc. Then, track image quality with more details like clag, tire marks and surface detail. Next, would be to add more people, who have more real animated movement. Flag men, perhaps? It would be nice to see the white flag waved on the last lap, then the checkered flag at the end of the last lap by real people. Then, real time weather effects, like dusk to night, rain to sunshine, and vice versa, snow, fog, haze, etc. Finally, vehicle damage and then online play, which I personally don't really care for all that much, which is why I listed them last.