Grid would have an impact on GT5 sales? How did you figure that one out, an arcade racer competing with a driving sim. No point in comparing Mario to GT5, Mario games sell more than any franchise, may that be Halo, FF, GeOW or GT could ever dream of.
Forza 2 was bundles, I know that as I got that game with my 360 so those numbers are pathetic compared to GT games, no matter how anyone spins in.