Guitar Hero was discontinued today.

According to its publisher, Activision Blizzard, development of the game has been discontinued, and the Guitar Hero business unit is being disbanded. The company cites dramatically falling sales numbers as the reason for discontinuing the game.

Music and dance video games, led by Guitar Hero, peaked at $1.7 billion in sales in 2008. But those sales numbers fell by 50% the very next year, and continue to remain low.

In a conference call with analysts, Eric Hirshberg, head of Activision Publishing, said that “Demand for peripheral-based music games has declined at a dramatic pace.”

The decline in sales included Activision’s latest releases, DJ Hero 2 and Guitar Hero: Warriors of Rock, despite positive rantings from game reviewers.

The company said this move will “reduce its exposure to low-margin and low-potential businesses.”

Activision also announced that they have canceled the development of True Crime: Hong Kong. They said they would be focusing on games such as Call of Duty: First-Person Shooter and the online role-playing game, World of Warcraft. At the end of last year, World of Warcraft had 12 million paid subscribers.

With the discontinuation of development on Guitar Hero and True Crime and their related business units, 500 people (7% of its work force) will be laid off.