That's a little harsh, isn't it? I'll agree that Hollywood has gone way overboard with the concept, but in some cases, taking a work from one form to another is a guesture of respect and love for the original. Most operas, for example, are based on other books and/or plays... does that diminish the opera?
Your question assumes that opera possesses intrinsic merits, a contention with which several FReepers would take issue. ;)
Seriously, that's a good question and one which I must ponder. For the sake of consistency, if I had to do it right this second, I'm afraid I'd have to argue that the original work is superior, if for no other reason than its originality.
My stance is indeed quite harsh, but then, no one's ever accused me of being a big softie.