Fairly easy to say since GT3 Gran Turismo is 2nd best, not by sales by definately by realism and review scores.
GT4 Meta lower than Forza 1. Forza 1 also had a better physics system.
Forza 2 meta higher than GT5P and FM2 had 360 hertz physics while GT5P could only manage 120 hertz.
FM3 has released with another great acclaim. Keeping 360 hertz whilst managing to stay 60 FPS and drastically improving detail. If GT5 is not 360 hertz, there is no contest for realism.







