Halo is owned by microsoft, it makes absolute sense that it would be an exclusive. They are using halo to push win8 just like they used halo 2 to get people to use vista.

I agree but still it is annoying for people that don't have a windows 8 phone or tablet

More annoying for people like me who supported Windows Phone 7 from day one and got no Halo love aside from the non-exclusive Waypoint app. I'm not supporting a platform that won't even give me OS update from version 7.5 to 7.8. Plus, dual stick shooters suck on a touchscreen anyway.