I think the original catalysts in favor of Vertigo were the following three:

1. Vertigo was seen by relatively few people as of January, 1973. It did not do big BO and probably most of those who saw it did so on the small screen in an edited version with commercials.
2. After its January 1973 TV showing, Vertigo was withdrawn from distribution by Hitchcock who owned the rights. It would not become publically available again until 1983.
3. After its withdrawal, a number of champions emerged claiming that Vertigo was the best film of all time but practically no one was able to check this out.
   So for years, many waited to see what was being touted as the best film ever made with no access to that film. So without a large number of knowledgeable detractors, Vertigo's reputation was cemented.

I think there is more to it than that. Nobody likes an "overdog" that seems to have been arbitrarily picked to NOT have much public sentiment towards it. Had The Godfather or 2001 or Casablanca or The Best Years of Our Livesor Psycho(which has been called "The Citizen Kane of Horror Movies") been picked, I think people would have understood. But Vertigo just never had the grip on audiences that those other films had.
Sight and Sound's poll which Vertigo topped polls mostly critics, academics, and directorsso it's elitist/anti-populist in its basic construction. Its current top 5 is Vertigo, Citizen Kane, Tokyo Story, Rules of The Game, Sunrise (1927). None of those ever set the US box office on fire. Vertigo is the most recent entry in the top-5, is the only one in color, and at this point is probably the only one of them that the average non-movie-buff might have seen. The only directors to get multiple entries in the top-30 are Ozu, Dreyer, Kurosawa, Coppola, Godard, and Tarkovsky (who gets 3). All of these apart from Coppola are terra incognita for most non-movie-buffs.
An intriguing paragraph that "cuts to the quick" about how Vertigo hit Number One on the Sight and Sound poll: its probably the MOST commercial film (and the most seen film) in a flock of art films and "foreign films"(well, to mainstream America as it dominated the movie biz for decades.)
That Vertigo is the NEWEST film in the top 5 begs (for me) the question yet again: when all is said and done, the motion picture may end up being a 20th Century phenomenon in terms of generating EITHER top drawer Hollywood films or important foreign art films(though on this point, I yield to swanstep on "what's happening now" in that regard. Do we have an Ingmar Bergman? A Fellini? A Kurosawa?)
To me an art film list is just this side of the paintings in a modern art gallery: not really directed to me as an audience, requiring a different set of "taste buds."
THAT said, I have great regard for the two American Film Institute greatest film lists to date one decade apart (1997 and 2007 as I recall.)
Will we get another decade's check-up in 2017? Or is the AFI done with this particular parlor game list?
The AFI list was composed by a mix of critics AND people who worked in the film biz. And thus movies like Psycho and The Godfather got right on it.
Funny thing though: the second list had more CRITIC participation so Vertigo and The Searchers moved right on up the list over the ten years. (I always lock Vertigo and The Searchers together among the least entertaining films of two entertaining directors.)
I don't think they'll do this again, but the AFI spent the early 2000's doing a "genre" list a year. "Psycho" famously and rightfully took Number One on the Thriller List of 100. "Some Like It Hot" from the year before Psycho took Number One on the comedy list.
I'm betting those lists hold. I'm betting the AFI doesn't try to do THOSE lists again.
So Psycho is Number One. Somewhere.

Vertigo, which is more of a personal art-film than almost anything else that Hitchcock made,
has recently been elevated to the position that Citizen Kane once had in film polls.and there's now a bit of a backlash to it for that reasons (nobody likes an overdog!).
I think there is more to it than that. Nobody likes an "overdog" that seems to have been arbitrarily picked to NOT have much public sentiment towards it. Had The Godfather or 2001 or Casablanca or The Best Years of Our Livesor Psycho(which has been called "The Citizen Kane of Horror Movies") been picked, I think people would have understood. But Vertigo just never had the grip on audiences that those other films had.
Sight and Sound's poll which Vertigo topped polls mostly critics, academics, and directorsso it's elitist/anti-populist in its basic construction. Its current top 5 is Vertigo, Citizen Kane, Tokyo Story, Rules of The Game, Sunrise (1927). None of those ever set the US box office on fire. Vertigo is the most recent entry in the top-5, is the only one in color, and at this point is probably the only one of them that the average non-movie-buff might have seen. The only directors to get multiple entries in the top-30 are Ozu, Dreyer, Kurosawa, Coppola, Godard, and Tarkovsky (who gets 3). All of these apart from Coppola are terra incognita for most non-movie-buffs.

In my view all of the 'big four' of Psycho, NbNW, Vertigo, and Rear Window
It is interesting how these Big Four have come to be known AS the Big Four.
Essentially, it is because in its two once-a-decade surveys to date, the American Film Institute has only listed those four Hitchcock films among the 100 Greatest Films ever made.
IMDb lists the four films in the four slots "known for" on the Alfred Hitchcock page, which may reflect reader voting.
I've always seen Hitchcock as having a "Big Three plus one":
The still-unmatched "three in a row" grand slam of Vertigo(1958), North by Northwest(1959) and Psycho(1960) are the Big Three, and all three have two collaborators that the earlier Rear Window does not: Bernard Herrmann for scores and Saul Bass for title sequences and, on Psycho, some visual consultation(storyboards for the shower and staircase murders; background clouds for the house.)
The Big Three rather climax Hitchcock's entire career in three areas of his story preferences: Vertigo climaxes the "twisted obsessive love" stories one finds in Rebecca, Suspicion, Spellbound, Notorious, and Under Capricorn. "North by Northwest" is the top of Hitchcock's "spy chase adventure" genre, preceded by The 39 Steps and The Lady Vanishes in the 30's and the WWII thrillers Foreign Correspondent and Saboteur in the 40s(with both versions of The Man Who Knew Too Much as forbears, too.)
And "Psycho" comes from Hitchcock's interest in the psychopathic personality. Its forbears are The Lodger, Shadow of a Doubt, Strangers on a Train , and, arguably Rope. "Psycho" also feeds from Hitchcock's ultra-popular TV show of the time, which often featured psychopathic villains.
That "Rear Window" inevitably makes it onto the list with the Big Three despite no Herrmann or Bass collaboration reflects the fact, I think, that Rear Window was Hitchocck's true masterpiece to that date, a perfect summarization of Hitchcock's cinematic techniques "put to the test"(POV shots, montage, camera movements) along with his classic "bickering couple" love story not to mention a pre-Psycho dollop of unseen blood and gore(is Lars Thorwald a psycho?) and plenty of dark humor.
But unlike the Big Three, Rear Window is a speciality number, whereas those Big Three "sound" in all the Hitchcock films made after them:
Vertigosounds in Marnie.
North by Northwestsounds in the spy films Torn Curtain and Topaz, and the comedy thriller Family Plot(written by NBNW scribe Ernest Lehman.)
Psychosounds in the horror of The Birds and Frenzy, and in the psychopathy of the killer in Frenzy(as well as in the "psychopathy" of the birds in The Birds!)
are A+ films, and choosing between them (say for the purposes of some survey or list or thought-experiment, e.g., which one would you take with you to a desert island if you could only take one?) is something that most people are going to fluctuate on.
I think Hitchcock biographer Patrick McGilligan wrote that these are the four Hitchcock greats, and which is greatest is always a matter of personal opinion. MeI'm not so sure. I think there IS one greatest film of those four, quite objectively. Psycho.
Vertigo, which is more of a personal art-film than almost anything else that Hitchcock made,
Yes, which seems to be why it has that critical adorationas against many, many, many more films in the Hitchcock canon that were much bigger hits with the general, worldwide, public. The elevation of "Vertigo" has always struck me as a bit of "critical contrarianism" to champion one of Hitchocck's LEAST entertaining and successful films as his best (albeit a film of great beauty, deep emotion, strong themes anda Bernard Herrmann score without which Vertigo would not be a masterpiece, I don't think.)
has recently been elevated to the position that Citizen Kane once had in film polls.and there's now a bit of a backlash to it for that reasons (nobody likes an overdog!).
I think there is more to it than that. Nobody likes an "overdog" that seems to have been arbitrarily picked to NOT have much public sentiment towards it. Had The Godfather or 2001 or Casablanca or The Best Years of Our Livesor Psycho(which has been called "The Citizen Kane of Horror Movies") been picked, I think people would have understood. But Vertigo just never had the grip on audiences that those other films had.
The simpler pleasures and achievements of Psycho are perhaps looking better to people now than they have for a while as a further consequence of that.
Well, of the Big Four, Psycho is the one that plays best TODAY. The shocks are still shocking enough, the perverse material "beneath the surface" still addles the mind and the overall look and feel of the film is nothing less than Classic in the most memorable way imaginable, (The House, The Motel, The Shower, Norman Bates, Mrs. Bates.)
I'm not sure I agree with the OP that Psycho is the ONLY A+ film Hitchcock made, but I do agree with the OP in that it is the Hitchcock film "above all others."
M

@lukemm. In my view all of the 'big four' of Psycho, NbNW, Vertigo, and Rear Window are A+ films, and choosing between them (say for the purposes of some survey or list or thought-experiment, e.g., which one would you take with you to a desert island if you could only take one?) is something that most people are going to fluctuate on. Vertigo, which is more of a personal art-film than almost anything else that Hitchcock made, has recently been elevated to the position that Citizen Kane once had in film polls.and there's now a bit of a backlash to it for that reasons (nobody likes an overdog!). The simpler pleasures and achievements of Psycho are perhaps looking better to people now than they have for a while as a further consequence of that.