What would happen if Gran turismo 5 and Halo 3 launched on the same day?

[Snake2]

I want you to imagine the following scenario both the Xbox 360 and the Playstation 3 are at 50m consoles sold. Both consoles have sold 25m in America and Europe to maintain an even playing field I have exclude the 'Japan region' so we are looking at the US and Pal region. So what would happen if both games released on the same day, with both consoles at 50m.

The Gran Turismo brand is strong in Europe while the Halo brand is strong in America. Interesting indeed 

Both games are 'HUGE' so what game would come out on top and why??

Please discuss.

 VS

Master Chief vs The Lamborghini