The music in Eternal Sonata is some of the best i have heard in both videogames and mainstream music. I guess it would only be expected of a game about music to have a phenomenal sound track, but a couple worth mention are the battle music, "Leap the Precipice", and a particular boss fight track, "Broken Balance". These two are, imo, the high points (and maybe kyoutenka), and it would be awesome to see them re-imagined via wailing guitars and such.
edit: this just occurred to me, there is a surprising lack of megaman 1's cutman area theme remixes. The one that is there however, is beyond awesome but still, its just one.