The depth and realism of Gran Turismo 4 was simply astonishing at the time. The racing was superb - but what really made the game tick was everything around it. It was a racing game where you could sink hours not racing, taking driving tests, upgrading your cars, hitting the oval to break speed records, watching an AI driving race for you in B-Spec mode.. so many ways to enjoy the game as short breaks between the highly intense act of racing. Superb soundtrack too. Masterpiece.