I really don't think you had the right idea this time around. First of all, I just didn't like the songs as much. That's totally an opinion, and I haven't unlocked them all, but I didn't find the instrumentals as catchy, I thought the alternative / punk songs were a little annoying (I could not stand "Fairest One of All") and the quality just wasn't what i expected. Secondly, I really don't think the direction you took this game was the right one; It's hard to appreciate the visuals when you'll mess up the song if you even glance at them, and I found it hard to appreciate anything but the comedy of boss fights - which was generally pretty short lived. So, while all of the graphical elements might have been better, and prettier, I don't think they enhanced the game. In fact, I think the overload of animation may have even slowed the game. I played the previous games in this serious with a pretty old computer and they ran fine, but this time, on a laptop with tons of memory and good graphics that's about 3 weeks old, it seemed that the path of the notes was sometimes not completely smooth which made it really hard to get the notes timed right.
My final issue is with "mistakes". It bothered me a TON that pressing the button a fraction of a second late counted as 2 mistakes (missing the note and hitting a key at the wrong time) and it drove me crazy when if my timing got off (due to the choppiness often) for just a second, I could amass 25 errors in three seconds.
I was good at SCGMD2, even better at the third one with most songs at perfect, and I really don't see myself devoting that kind of time to this game. I am thoroughly disappointed.