This one is certainly a classic that helped start a whole new generation of gaming.
I just recently played through this game as my younger sister has it. She has a lot of trouble getting through the whole game so I helped open things up so she could, at least, practice all the music. :)
At this point my opinion with GH is that is simply overdone and after playing through a handful of the series I think they have generally done a poor job of actually improving the game from release to release.
When I played GH I was sort of shocked how exactly the same it was to every other game in the series I have played. Indeed, this game set the stage for a whole new type of gaming experience BUT you'd think they would advance things enough that you could actually tell the difference. It's sad to say that you can barely distinguish at all which GH game you're playing because they're all so identical.
I will give this game a 9.0 because of it's role in doing some new things in the game world. However, at this point, I certainly won't be playing any more of the series. GH is certainly a classic but it would be nice if they REALLY made some new stuff. I know World Tour has a new experience added but I feel this comes more out of necessity than desire.(thanks to Rock Band)
It's a good game BUT if you happen to have played any of the other GH games there isn't anything big about this one at all.