More like the powa of having 6-7 years of development time with an unlimited budget.
GT4 was released in 2005.
And it's not like GT5 is the first game that got that treatment. There are enough games with long development time. And a lot of those games ended up being pretty shitty, or look like shit.
Polyphony Digital is a very talented developer and a perfectionist. GT1, GT2 , GT3, and GT4 are all excellent games and were released pretty fast after each other.
It's just that PD is taking their time with this one, and it shows. There's so much content in this game.