This is too much low poly even for Iphone !
And don't forget mobile platform are growing in power :
Iphone 2, Ipad 2 etc ...

Your models only would be good for display in far distance with LOD, but you need lot more detail for car near the camera !





Don't forget this beautifull game is running on a tiny Iphone
, and not a Bigpowerfull PC with A8 !
So 3D art really matters, not only power and engine.

So make somehting really good looking, go to hard work
(post on Polycount forums , people will help you on making
something better and great) !