The reason music games tanked isn't because there were a ton of them available, it's because there were a ton of them available and they each cost $150. If you had to buy a $100 peripheral to play Halo that didn't work for Call of Duty, FPS games wouldn't sell very well either.
Wii has more 20 million sellers than PS3 has 5 million sellers.
Acolyte of Disruption