Guitar controllers:

Wii Balance Board:

Wii MotionPlus:

Sony Motion Controller:

Project Natal:

Wii Vitality Sensor:

I think the Balance Board will get more games.  It's already closer to PS3 sales than the PS3 is to the 360, and it has Tetris, and even Mario and Sonic at the Olympics uses it.  I think MotionPlus will be a distant 2nd, followed by everything else.  All the new stuff seems to be launching too late in the consoles' lives.  Out of the new motion controllers though, I think MotionPlus will have the most games, just because it launched first and is the cheapest, so more developers will be willing to take a chance on it.

I think it depends on the sales of WSR.

I don't think many games will *revolve* around Motion Plus, but I bet a hell of a lot more games will support it than the Balance Board. In fact, probably many many games will.

The balance board currently has the most support at this moment.  Really it's just a matter of seeing if WM+ can catch up to it.

The rest don't matter.

Do you mean rich decent quality... well I can see nintendo support wii motion + and the balance board but there seems to be very good third parties that seems interested in sony's wand and microsoft natal... but then it all comes down to sales so I think the first two what the ghost said :)

Easily the Balance Board, simply because it's more of an option then a necessity in some games. (See Punch-Out, Mario & Sonic at the Winter Olympic Games and others)

Motion Plus, i think. Unless Sony makes good on their idea to start patching PMC functionality into PS3 games.

Pretty much this.

Rhythm games are starting to phase out. I think.

MGS4!

Whats PMC? PS Motion Controller? I thought Private Military Corporation

Am I the only one that thinks it's the guitars? I mean they span four different platforms and get anywhere from 6-12 releases per year on each platform they're on.

Wikipedia lists 33 games that use the Balance Board, either currently released or announced.  So that's 33 games in just under 2 years.  The guitar controllers have been around for just under 4 years, and I can think of 10 main Guitar Hero games (1, 2, 3, 4, 5, 80s, Smash Hits, Aerosmith, Metallica, Van Halen), and 4 Rock Band games (1, 2, Beatles, LEGO), not counting the handheld versions for either.  Unless I'm forgetting a bunch of games, I don't think Rock Band has 20 or more track packs, so I think the Balance Board is the winner here, so far.