Not sure there is any "universal way" to know if something is amazing, as there will always be someone who doesn't get the proverbial joke, whatever the joke may be. Which isn't even a burn on the someones; nothing can appeal to absolutely everyone. There must even be a sad few who would watch Shawshank Redemption and find it not a comment on perseverance and spirit, but an inappropriate glorification of prisoner life. =P
To your original question, and if I'm honest, Birdman has become my favorite film, because I find my self still drawn to its art, still considering its mirroring of questions which can only be unanswered in real-time but which likely shouldn't be ignored. My favorite thing about it is probably the way that it built a story which lives not "in real life", but in the psyche -- because in the end, that's where we all really live. It's a prism through which persons who are so inclined can examine their own relationship with various elements of reality, and of hyper-reality. As such, it ain't for the faint of heart.. to wit, I think a lot of the misplaced anger about this film (amazing the reactions it draws...) comes from some understandable frustration.
However, I can't quite decide if I prefer it to Hal Ashby's Being There, which to me is still the loveliest (and oh so humorous) tap on the shoulder with regard to conscience and humanity, and the complications of traveling about with a pure heart amidst the ensnarements of modern society.
“A most powerful being, an unknown sage — he is called Self. He inhabits your body, he is your body.”
— Friedrich Nietzsche
" narratology" -
1) Have you thought about / explored the influences that abound, especially Shakespeare? There are many flat-out allusions, and far more kind of latent-type allusions.
2) Not for nothing, but really responding because you brought up The Shank and seemed to suggest that it's seen as "a comment on perseverance and spirit" by most who like it? I know it has a following and I did enjoy it myself; I also read the Stephen King 'novella' and taken together, it is obviously Stephen King's 'fantasy fulfillment' of "What would it be like for someone like me to go to Prison - and be The Hero of The Prison!?!"
Stephen King, unlike most [esp male] popular writers, does not 'make the main character / narrator that specific Hero Type' - and when he finally created The Shank, he most obviously based The Hero on his own fantasy of what a true Hero would be like; as well as a highly inaccurate portrayal of Prison and Prison Life and Prisoners.
So when a totally unreal, fantasy world is created and then populated by characters who are realistic enough to fool many movie-goers, people seem to actually take it seriously when it's simply very well-done Manipulation just like all of the others.
Just a thought - my immediate reaction for which I found a lot of support... (and I know it is Sacrilege to many to ever, ever Put Down THE SHANK!)