Now with the benefit of hindsight, weren't the prequels bound to suck on some level? You're going to take a movie franchise that is revered by a generation and revive it with almost completely different characters and set it before the other films so that every meaningful aspect of its story outcome is already known by the audience. You could still make that entertaining but it's going to depend on your success at creating interesting new characters (Lucas doesn't do characters well, he does archetypes well), making the refreshed characters like Yoda and Obi-Wan work and then making their journey to the forgone conclusion an interesting one. But that's not all, you also have to stretch this tale out over three films, each of which has to have its own internal story arc that will satisfy the audience.
I just think that was bound to be a let down for so many reasons. Add to that the fact that Lucas was apparently writing the story one episode at a time and it comes out a bit of a mess where we basically have a new villain in each film, old characters grafted in for no apparent reason (the SW universe starts feeling a little claustrophobic when the same wookie, bounty hunter and hutt turn up at unconnected points in the story) and much time is spent on the boring details of Palpatine's deception. Okay, we can see that the whole invasion of Naboo is just a set up to help Palpatine get into power, we already know that Amidala, Anakin and Kenobi will live and Qui Gon and Maul don't have any impact on the overall plot of the original trilogy, so where's the suspense? Who even cares who wins that battle?
I don't actually hate the prequels, but I do think that they were pretty much doomed to suck at the idea stage of development.