I think to ask what the definite Broadway show is, is kinda asking who the best actor in the world is. It's completely up to people's own personal taste. Like for me, although it has it's problems, personally WICKED is the best Broadway show I have ever seen (and I've been a Broadway nut since 5) but there's plenty of people on this site who would say the exact opposite. Just like how so many on here think GYPSY is the best show, yet I, even though I do love it, think it's rather blah.
I think what makes a show become such a massive hit amongst audiences (Such as Phantom, Les Miserables, WICKED) is that those shows have that "it" factor. We can sit and dissect each show and place things in the "good" box and the "bad" box for hours yet we will never come up with a for-sure answer. It's combo of all those things (book, score, actors) but what makes them so different is, as I said, that "it" factor.
"Life in theater is give and take...but you need to be ready to give more then you take..."