In all of the iOS universe, no other app comes closer to sounding like a real guitar. It departs from a real guitar when it comes to how it is played, but that is a VERY GOOD thing, because trying to shape chords and fret strings on a touch screen is annoying and stupid. If you only get one guitar app, this should be it. If you have more, this should be at the top of your collection!
ZenLizard about Guitarism - Pocket Guitar