Let me stop you first before you begin reading this brief story. This isn't a tale about how a 6-year-old became so good at the video game "Guitar Hero" that he is now joining the Led Zepplin revival tour.
While "Guitar Hero" is an option for someone who is mildly interested in the guitar, it's not going to be a "Stairway to Heaven" and teach actual chords and music. A Fretlight Guitar, however, could be the answer to teaching yourself how to play.
From the website, the product is a real, six-string electric guitar that uses an interactive light system, which enables the player to learn notes, scales, chords, etc. It comes with initial software to get started, and there are numerous other applications (both PC and Mac) that work with the system as well.
A video game is much, much cheaper, as the guitar models run $400-900. In the end, it comes down to whether or not you want to learn the instrument, or you just want to play around. If you're ready for the real stage, Fretlight might be your next step.