Yeah X3's music... well I think it's terrible, to be quite honest. I don't think I'm in a minority on this one either.
Yeah I don't like 7/8/R&F's thing where you have to beat bosses in a certain order - it seems to totally go against the whole concept of playing the stages in whatever order you want. In 7 at the very least, you can use a password to have all eight unlocked from the start, which skips the needless intro and middle stages.
I played a fanmade NES demake of MM7 once, and I think it's actually far superior to the real MM7. It plays exactly like if MM7 were actually an NES game, so I consider it good enough to be canon, but I haven't played it enough to be familiar with it or know exactly where I'd rank it. I think I'd rank it higher though, it's just a more fun game to me. It doesn't fix all of the problems I have with 7, but it does fix many of them, such as Mega Man looking and playing correctly, the boss order being semi-predetermined, and the music being bad (it's still not great but it's better). The bosses are also improved, too, since they no longer reset their attack patterns stupidly when hit by their weaknesses. They're still pretty easy though and the weapons are still bad.