Why must it be exclusive?
Because all good Sonic games are exclusive.
Sample:
QUOTEKikizo: I am not sure about the extent of your personal involvement in the new Sonic on Xbox 360 and PS3, but you must be aware of the issues the game has in terms of glitches, control problems and loading time. One thing a lot of customers have been asking is, how these issues can be in the final product, is there anything you can comment on in relation to this, for example the QA [testing] process of development?
Ogawa: The reason why we probably ended up with what we see today, involves a lot of reasons. One is that we did want to launch the title around Christmas, and we had the PS3 launch coming up, but we had to develop for Microsoft's 360 at the same time and the team had an awful lot of pressure on them. It was very hard for the team to try and see how we were going to come out with both versions together with just the one team. It was a big challenge.