Xbox 360 and Wii in my house as well, my 11 yr old son plays the Xbox exclusively (FPS games) while my 8 year old son plays the Wii but also enjoys the kinect games on the Xbox.

I like the Kinect sport games more than the Wii games.

I would suspect that once a game console makes its way into a house a second won't be far behind.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70