Damn it Funk, now you made me browse Youtube for the old Final Fantasy songs! Ah, how nostalgic...Ahem.
Now that I think about it, I can't remember any interesting music from non-JRPG games. It's a bit sad really. We really do need some more memorable songs for our games.
I don't really play MMOGs, so not much to say there. Although, adding some mighty boss battle song might not be only good. Part of the reason for the attraction for boss music in RPG, is that you hear then only ONCE in that "epic" battle with the evil beast of evilness after you have worked so hard to get to it.
In a MMOG, you can usually come back to the boss quite effortlessly, hear the same song again and again. After a while, it would really start to annoy you and become dull. That is not the desired effect of the song, quite opposite of it.
Maybe if the would be an option to hear different songs for the same boss, so it would not become stagnant...I don't know.