After watching the video in this ( http://www.vgchartz.com/forum/thread.php?id=45452 ) thread I started to understand what was interesting about Wii Music and why someone would enjoy the game ...
Being a drummer who uses a digital drum kit, I generally find myself playing along to other-people's pre-recorded music and yet I rarely ever attempt to play the song in the way the other drummer did; there is an enjoyment that comes from this that is related to being able to create what you heard in your head. Now, I'm not a particularly good drummer, and it took me years to become a decent enough drummer to be able to think of interesting ways of playing a song and to be able to pull it off; the average person is not going to put in the time and effort towards learning music in order to get to the stage where they can enjoy creating something.
Miyamoto is an accomplished guitar player and probably started out trying to create a game which captured the sensation of creating music for people who do not have any musical training. How ridgid the game seems to be can (probably) turn off some people who are fairly good musicians because they will be unable to bend/break the rules to create the songs they want to make ... At the same time, the free form (and sandbox) nature of the game will probably frustrate people with little experience and/or imagination because they will be unable to see any point to playing it. In the middle ground (where there are still tons of gamers) Wii Music will probably be an enjoyable game for quite a few people.
