Kind of a silly debate, because it didn't happen that way, it is impossible to really know.
I am of the opinion that if The Phantom Menace was released in 1999 exactly as it was released, but without there ever having been an original trilogy, it would have met poor box office success. It would have been considered on par with most other kids action flicks. Without Star Wars having been a known and popular series, I really don't think it would have generated a whole lot of attention. Very likely sequels would not have even been made, but then again a lot of crappy movies get sequels. Of course, the prequels were so closely based off of the OT, it would be hard to imagine them existing without the OT having come first.
It is harder to imagine this scenario taking place back in 1977. Like someone else mentioned, it would be just another sci-fi movie. But it would have been a different movie entirely than the one we got.
Anyway, even if this was the case, I am not sure we would be complaining about the OT, which I guess we would call the ST, sequel trilogy. If it was as badly done as the PT was, then yeah, we might have a few gripes, but it really wouldn't be a big deal to me. Sequels continue a story, there are countless crappy sequels, but they are not near as annoying as prequels, because prequels go around and change the story you already new (to use a non SW example, we can look at ST: Enterprise. There was an episode where they ran into the Borg and nearly get assimilated all these years before Picard made first contact with the Borg, which was suppose to be the very first anybody knew anything of them. Another episode had them run into some Ferangi, when once again, Picard and his crew go on a diplomatic mission to make first contact with the Ferangi all so many years later. These things screwed with continuity, and it pissed off fans. The PT did this same thing.
If there are any movies I dislike as much as AOTC, it is Terminator 3, and Alien Resurrection. Those are two other series I like alot, and both those movies are among the worse sequels the history of sequels has to offer. I simply do not watch those films, and my enjoyment of those series goes undeterred. For some reason, the prequels don't work the same. After seeing the two Hayden Christenson prequels, it was really hard to see Darth Vader the same way again.
Also, rcb, your theory seems to think that we hate the prequels simply because they are not the OT and for no other reason. This is why your logic tells you that if the PT=OT and OT=PT, then we would hate the OT and love the PT. But this is forgetting the important fact that the PT films were simply terrible awful films, from writing, to acting, to the very way they were filmed, they simply sucked. If the hypothetical OT that came out when the PT did because the PT came out when OT did, sucked as much as the real PT did, then I am sure many of us would have hated it, but I am sure we would not still be talking about it.
Hmm, hypothetically speaking, is the hypothetical 1977-83 PT on DVD in its original unaltered form and in anamorphic widescreen?