How's this for embarrassing: music-based videogames sold so poorly this year that they singlehandedly dragged down the entire videogame sector.

According to data compiled by the NPD Group, music-game sales fell to $70 million this past December, compared with the $225 million they raked in the year prior. Music game sales for the year totaled only $291 million, compared with $876 million in 2009 (and close to $1.7 billion in 2008).

In a research note, Wedbush Securities analyst Michael Pachter said this "softness [accounted] for all of the industry's software sales decline" this year, and more than 80% of the decline since 2008.

Software sales mean game sales, and according to the NPD figures, December's holiday results provided little lift despite relatively positive October and November returns. Both videogame console and game sales were down compared to December 2009. Console sales for the month fell 16% from the year prior, while game sales fell 8%, according to data from the NPD Group. That capped an overall disappointing year for the industry, with 2010 console sales down 13% and game sales down 6%.

But there were some bright spots. Microsoft's Xbox 360 was the only game console that showed any year-over-year growth, thanks in part to the Nov. 4 introduction of the new Kinect motion-based controller, which moved some 8 million units, according to Microsoft. Wedbush's Pachter estimates half of Xbox 360 units sold in December were bundled with the Kinect device.

Also, the new breed of dance-based titles are starting to see some traction. Ubisoft's "Just Dance 2" was the second best-selling videogame of the month, with a reported 5 million sold, according to Ubisoft (NPD no longer releases game sales figures). Only the blockbuster "Call of Duty: Black Ops" ranked higher. For the year, "Just Dance 2" was the seventh best-selling game.

Another Ubisoft dance game -- "Michael Jackson: The Experience" -- ranked eighth for the month. Both are available only on the Wii console.

Harmonix's "Dance Central" for the Kinect was a critical hit, but didn't make the charts, likely because there are only 8 million Kinect devices out there to support it, compared to the Wii's installed base of almost 40 million.

Curiously, none of these dance games are grouped into the music-game genre that has been pegged with the industry's decline. That's odd, because they resemble games like "Rock Band" and "Guitar Hero" in almost every way. However, it's unlikely dance-based sales would have had a huge impact on the genre's stunning decline.

Both types of games ask gamers to interact with a song in a rhythm-based fashion. Both contain huge soundtracks of licensed master recordings. And both let gamers buy and download new songs to "play" with via in-game stores. The only difference is that "Rock Band" and "Guitar Hero" require special instrument controllers, while the dance games rely on motion-capture controllers like the Kinect, Sony's Move, or the Wii Remote.