The first game on the PS2 and Xbox was quite poor and had a lot of flaws. The demo of the second game on the 360 doesn't hold much hope for an improvement. I don't really thing there is anything to get excited about.
This game discussed in this topic matey, as in Juiced 2. I have downloaded both, the custom car stuff in Juiced is quite good I thought, chafftastic cars but good none the less, but game play is on par with the PS3 Nascar demo.
GT5P on the other hand, now thats a racing fan game ...
Just my personal feelings, but thats what forums are all about.