after the first 10 weeks gears of war 2 only sold 1.6mil in 126weeks
after the first 10 weeks halo reach has already sold 2.2mil in 32weeks
gears as a franchise has no legs. Even gears of war 1 had pathetic legs compared to halo considering gears was a new ip and came out very early in the 360's lifecycle while halo already had a huge inital following and came out after quite a few xboxes have been sold.
after the first 10 weeks gears of war 1 only sold 2.7mil in 228 weeks
after the first 10 weeks halo 3 sold 5.3mil in 182 weeks
While initial sales might just be comparable to halo reach. Its legs will be laughably worse. I'm comparing it to halo because halo is an established xbox exclusive that's mainline games are or will be consistant 10mil+ sellers for the 360.
8mil ltd is the max gears of war will reach. Can't really be compared to kinect because kinect is a brand new thing while gears of war is an established ip that has already had 2 very well recieved games.