It pains me to give a 3 out of 5 stars to a game like this one, but I think it`s necessary.
The idea is brilliant, and the way you presented this concept is extremely entertaining. You planned this game very well. Whoever starts playing won`t stop so soon. The chievos, the bosses, the new guitars, the graphics, the songs...
Bosses battles were an amazing idea to add to the action. And since there are chievos for playing the game for 3 hours, they made a very practical way of keeping things interesting - it was like pouring nutella on good candy bar.
I also like the animations on the lower side of the screen. They can be distracting at first, but it just made the challenge more interesting in the end. The new guitars redesigning the track is also very fun.
All perfect, this is great...
Or "should" be great. Considering a game with this level of quality (graphics, songs and general idea), the least we would expect is outstanding commands control and frame rate (I know it`s not lag on my PC, the frame rate is actually pretty terrible dude).
I don`t want to be rude or anything here, but you forgot that people must be able to play the game. In addition to the frame rate, I experienced many notes that didn`t match the song (some were too fast, others too slow). In gameplay aspects, SCGMD3 is way better than this one. I don't quite know how to describe those problems in technical terms, but I'm sure you can get what I'm talking about.
If you guys were able to mix up these ideas, graphics and design with the gameplay you have on SCGMD3 (even better, try to improve that even more) this would be a total 5/5 and probably one of the most fun, creative and entertaining games here on NewGrounds.
I hope you find this useful somehow.
Keep up the good work!