FWIW, The Planets composed a much better piece than 4’33".
So to answer the OP: it’s garbage AND genius. Garbage because it consists of throw-away sounds. Genius for conning people into twisting themselves into knots trying to come up with a rationale justifying it. In doing this, Cage was an artist. A con artist.
As Orwell wrote in a different context, “One has to belong to the intelligentsia to believe things like that: no ordinary man would be such a fool.”
From threeorange’s 2002 link:
That’s quite a gesture.
Um, no; that there is* original work*. 
(I was a performance art major at the Art Institute of Chicago, so I have the lingo down pat.)
If 4’33" was the only thing that Cage ever contributed, you might be right. But Cage was not just some prankster who put a chainsaw into a sofa and tried to pass it off to a museum as art. He was a career composer, and spent a good deal of his early career doing more traditional (and well received) compositions.
4’33" stemmed from philosophies about the essence of sound (or rather, the fact that there is no way to escape from sound), over which he had been pondering for years.
I haven’t ever performed 4’ 33" (deliberately, anyway) but I have performed ‘The Wonderful Widow of Eighteen Springs’ once, and the ‘Aria (any voice, any range)’ three times - once for a recital in 1983, again as an audition piece in 1990, and as part of a recital in 1994.
‘Wonderful Widow’ (1942) is for voice and prepared piano, though the piano isn’t so much prepared as the lid is shut. It’s essentially a percussion part played on a closed piano, which is the kind of thing Cage loved to do throughout his career. The ‘Aria’ is twenty pages of squiggles with little black boxes every so often. The squiggles are in ten different colours, and represent ten different styles of singing. The text alternates between English, French, Armenian, Russian and Italian, with some random clusters of consonants and vowels. The black boxes represent any non-vocal sound - percussion, tape, electronic sounds or ‘non-vocal’ uses of the voice. It is intended to last approximately ten minutes.
One of the hardest things about performing his music is the challenge it presents to your own aesthetic and work ethic. Throughout working on the ‘Aria’, I was conscious of the fact that I was busily constructing a story and a through line out of something that had been deliberately composed without an inherent through line. Each time I’ve performed it, I’ve started from scratch, making different choices as to the sounds I’ve made. I kept my notes from the last time, but they’re packed right now, so I won’t be able to look them up for a couple of months. (In light of the organ piece, that’s pretty soon, really.)
I do remember several sessions where I just felt so angry at the work that I was having to do; work that would normally have been the composer’s job. I also remember how proud I was of those performances because there was so much of me in there. I wish more ‘Classical’ composers would trust the performers that much, and I always want to justify the composer’s faith in me…
So, yeah, I think Cage was closer to genius than to garbage. Certainly, 20th century music would have been a lot less interesting without him, and to me, he epitomized, along with Warhol, the 20th century idea of ‘make your life a work of art.’
So the context says it wasn’t a con? Then the context is a con.