The best Guitar Hero: On Tour game. It trumps the first one in every way.
The gameplay hasn't changed much since GH:OT. In fact, it's almost the exact same. The only difference is some more game modes. But, these game modes make this game a whole lot better than GH:OT. You can play as the Bass Guitar in addition to the Lead. So, if you're bored of playing as Lead, you can turn it down a notch and play as Bass. Also, while GH:OT had 26 songs, this game cranked it up a bit (and I mean, a bit), and ended up with 28 songs, with 3 bonus songs as opposed to 1.
The graphics are improved a bit, but was just enough to make the game seem closer to being eye candy then ever. The rock meter is a lot more awesome, and the guitars have gotten more creative. In addition to a few other things, like the menu.
The sound quality is still sub-par, with some indistinct lyrics. But the soundtrack is better, like I said. It has some songs from Guitar Hero: World Tour, like "Sweet Home Alabama" and "Satch Boogie", and some of it's own songs.
The replay value, is slightly better than GH:OT, just because of the new songs and new modes. Asides from that, the replay value is average.
Overall, if you are new to the GH:OT series, but want to stay away from GH:OT, take this one instead. It is a lot better than GH:OT in many ways. If you like the first one, Decades is worth a try. If not, stay away from this one.