It seems many people don't really know of Miracleman, Moore had established many of these concepts within this series before Watchmen, and before The Dark Knight Returns as well. Before Ronin, before Moore's own genre redefining work on Swamp Thing, before almost anything else there was Miracleman (or Marvelman) in 1982. If people are going to discuss the point at which "superheroes" "grew up" or became serious works of literature, I cannot see any other candidate than Miracleman personally. TDKR & Watchmen also deserve massive credit, previous posters have summed up the extent of that credit very effectively.
I don't personally see any problem with these Watchmen prequels, if they are done well, but it remains to be seen if they will be or not. It is quite a gamble to be taking with such an epic & monumental book as Watchmen.
What I see as a real shame is that DC didn't take the opportunity with the resignation of one of Alan Moore's nemesii, Paul Levitz to try & extend an olive branch to Moore. Why not give him everything that he wants & try to make piece with him? Giving Moore rights to the original Watchmen does not have to exclude DC's options to expand on the Watchmen universe as they are doing now. It would give a much deserved ownership of a work to the single most important writer in the field of modern comics. Comparing the characters Moore created for Watchmen to the ones he revamped them from is completely laughable. Like comparing Luke Skywalker to Flash Gordon, who was part of Lucas' inspiration for Star Wars.
The greatest tragedy for me, bar none, that came out of this long running war between Moore & DC executives is that Moore refused to work for DC after it.
It is a tragedy to me personally that I cannot get to enjoy Moore's work on Superman or Batman, or even more importantly, Swamp thing, and one of his many incredible creations, the incomparable John Constantine.
While Moore "swore" never to work for DC again, he did publish The League Of Extraordinary Gentlemen & other titles with his friend Jim Lee after DC had bought Wildstorm & ABC comics from them. Perhaps if DC were to treat Moore with the respect that he deserves, he may come back into the fold one day & we will all be better off.
Although not everything Alan Moore creates is incredible, he is certainly one of the most incredible writers & creators ever to work in comics.