Let me show you why the Guitar Hero franchise is so popular.
That guy looks like a rock star.
Now let me show you why Guitar Hero doesn't work on the Nintendo DS.
That guy looks like he's getting real time stock quotes on his Blackberry.
If Guitar Hero was just about the music, On Tour would be fine. It's not he most comfortable game in the world to play. The buttons on the guitar grip are small and the whole thing can be difficult to hold on to sometimes, but it works, however awkwardly. There's a decent selection of songs, some from GHIII, some new to the series, and the sound isn't awful.
But if Guitar Hero was just about the music, players would play it sitting on their couches holding standard controllers just as if they were playing Halo or Madden. Guitar Hero is about strapping on a plastic, 3/4 size guitar with no strings and feeling like you're Jimi fucking Hendrix, not some guy who sits on the couch all day, controller in hand, playing Halo and Madden.
In that sense, the only sense that matters, Guitar Hero On Tour is a complete and total failure, even with "We're Not Gonna Take It."