I think whether a version of a song is 'definitive' or not is entirely subjective, so agreement can never be reached. There may be people who think (say) Elvis Presley's version of White Christmas is the definitive one. There could even be a large of people who think so, but they are probably outnumbered by those who would say Bing Crosby's is the definitve one. None of them are wrong, because it's every individual's call. Basically a 'definitive' version of a song is the one an individual thinks is the 'best' one.

So, I'm not really sure what we are debating here?