One thing people don't seem to consider is this. Maybe the physics were off and everything was actually harder to control then it would be in real life. Now they may have improved the physics closer to real life which may actually be a little easier to control and everyone says they are wrong. Until someone takes each car in the game and real life, sets them up as closely as possible and imitates every situation in real life and the game none of us will know for sure. Alot of things people are forgetting are such things as LSDs, traction control, ABS, etc. Alot of cars in real life come with these features and don't necessarily have a way to turn them off like the game. If you watch shows like Top Gear there are times when they are flailing these cars around the track and they talk about all the grip that a car will have, they're doing slides and what not, but they're managing to keep it under control and they aren't acting like it's a huge struggle to do it. It's not always just the tires that play a role, it's also the weight, shape, aerodynamics, balance, etc that changes the way a car handles. Alot of people say Forza had fantastic physics, but cars at times especially rear wheel drive cars at slow speeds where way to easy to lose traction in, even with better tires. Alot of people haven't played GTR, but people will say GTR is a better sim. It's primarily because they make it into a straight get on the track, here's the guy telling you to go in the pit, giving you updates, etc sim. That doesn't mean the physics are more realistic, it just means it's more geared as being a racing simulator.
Besides GT must be doing something right if the auto industry is eager to have people take a virtual test drive of their car in GT. If the car's handled nothing like real life I can't imagine the automakers being too eager to let you take a drive in their car that's not even close to the real thing. They want to show you what it's like to drive it, and what makes their car special.