Let's be honest: Guitar Hero isn't a console franchise that's got 'mobile hit!' stamped all over it.
Why? You can't plug a guitar peripheral into your phone, most handsets are still a bit rubbish when it comes to in-game audio, and you can't really recreate the social elements of the console version (i.e. the showing off to your mates with star jumps, knee slides and Status Quo-style synchronised riffery).
With that in mind, Guitar Hero III Mobile should be a big disappointment.