Grand Turismo 3 was my last installment in the Gran Turismo series because I found it to be very pretty but shallow ... I'm not a fan of simulation racing in general because I find this is a common failing of the genre.
With that said, when you're spending (what has been rumoured to be) over 5 years and $100 Million to develop a game and your competition releases 3 $20 Million games in the same time your game better be dramatically better; and sell dramatically better too. If you spend dramatically longer and dramatically more money to achieve an incremental improvement you have really been wasteful.