[johnny]

I really don't think it's possible for anyone to say "I always prefer the original over the cover" or "I always prefer the cover over the original"

I think Madonna's cover of "American Pie" is a travesty, an assault on mankind and good taste, and no one could ever convince me otherwise.

John Cale's cover of "Hallelujah" - and, in fact, many of the covers of that song, which is so beautiful that I think it actually transcends whatever artist sings it - is as good as the original, though I prefer Leonard Cohen's strange poetry-singing for some reason (I should note, I heard John Cale's version before Cohen's).

Limp Bizkit's cover of "Behind Blue Eyes"? Another horrible, horrible thing.

Richie Havens's cover of "Here Comes The Sun"? Beautiful. I actually prefer it over the original Beatles version, and I am probably the biggest Beatles fan anyone on this site will talk to.

I agree with Quiet Man Cometh: the good covers are the ones that add something new to the song. A new emotion, a new stanza of lyrics (in the case of "Hallelujah", which tends to get a different stanza for each cover, as there are something like nineteen official stanzas written by Leonard Cohen) or even a new tempo is good. When people just make cheap, sickening covers to cash in on an old classic, that's when the cover upsets me.