It's not *inferior*, it's very different.
The first two are robotic response games, wonderful and rewarding but where your skill comes from pattern recognition, and the relationship between that set pattern and the music. (Please don't mistake this for criticism, Band Brothers and Rhythm Heaven GBA are two of my favourite games).
Wii Music is a jazz performance simulator where the skill is in creating your own version, and the reward is not from a score or a medal but from the player's own satisfaction at their achievement. Somewhat like a time-attack means the player will re-start as soon as they are unhappy with their performance on a lap, so will a Wii Music addict repeat the same exact section of music until they have it sounding just as they like.
That's not inferior. It's just very very different and trying to put it in the same category as rhythm-action games surely creates a large amount of the misunderstanding.