This is my proposal. I liked the idea of doing it vertically as most of the photos I found show the XBOX 360 in this way. I thought that by showing the button as a feature of the machine, it'd avoid confusing the flyer with one that promotes the machine itself. Finally I though it was cool to play with the phrase "Begins..." and the start button.
I used a 1/4 of a A4 piece of paper and I have a version in high resolution 300 dpi CMYK.