When was Guitar Hero first made?

The first Guitar Hero release was 8th November 2005, and Guitar Hero II was relase 7th November 2006.

The previous answer claiming 2007 as the release date was the year for Guitar Hero III, made available 28th October 2007.

Guitar Hero and Guitar Hero II were developed by Harmonix, but the rights to the series was owned by Red Octane, and with the aquisition of Red Octane by Activision, Guitar Hero III onwards has been developed by Neversoft, with ports to other platforms done by other companies.

Harmonix have since gone on to create their own rock based music game series called Rock Band, the first in the series was released 20th November 2007.