GREATEST is subjective term and should NEVER be confused with "biggest grossing" or "most expensive".
Take a look at the
10 most expensive photos sold (often at auction)
The Billy the Kid photo's value is concentrated in the historical worth, not the "art" of the image.
2 are Cindy Sherman self portraits (or Selfies as the grownups trying to sound hip are calling them today)
The Pond/Moonlight, by Edward Steichen has historical significance and is an "early master". It's also 1 of only 2 prints of the image (both hand-colored). It isn't his greatest work.
3 are contemporary "landscapes" by Andreas Gursky.
One is a plagiarism from a Marlboro cigarette ad.
On the whole, none of them qualify as The Greatest Photo.
Unfortunately “GREATEST” is always confused with “biggest grossing” or “most expensive”. Take the recent thread about the Eagles being the reason for a domestic violence incident. Jokes, links to Big Lebowski (”I hate the Eagles!), dissing the Eagles, and one poster near the end persuading us, of God only know what, by citing the number 27 million (copies of greatest hits sold.) Note the sometime weekly threads of highest grossing movies in the past weekend. So what?
If anyone believes any of that, he oughta run to the Amazon bookstore and buy the latest by Danielle Steel (and all the 100 previous “novels” of hers.)
I happen to like Andreas Gursky, and think that he stole his style from me (I certainly didn’t steal it from him, having only heard of him in the past several years.) His photographs are interesting and expressive, and that’s enough for me.