The bonus songs (the ones you had to buy) were original, as was "John the Fisherman" by Primus and "Stop" by Jane's Addiction. All the others were covers, which included some horrendous covers of "Heart Shaped Box", "Sweet Child of Mine", "Killing in the Name" and "Hangar 18".
In their defense, they've got a guy who does a damn good Ozzy, and there were a few good covers in the game, but most of them were bad, that's why I'm not getting my hopes up for GH3