The potential for an amazing story was very high with these prequels if they'd been written by a talented writer. The fall of the republic, the decay and eventual destruction of the jedi order, they had history like that of the rise and fall of the Roman Empire to draw inspiration from.
I think we all had this amazing backstory in our heads after watching the OT and hearing about a Prequel Trilogy being made, an ancient decadent republic on the verge of colapse, an overly complacent/proud jedi order, the tragic fall of a noble hero, controlled by his own fears of loss, trying to do whats best, believing the ends justified the means, only to lose his path along the way.
Instead we got an unlikable petulant man-child as the main character that we were supposed to be rooting for, tedious stories of trade embargoes, stilted automatons for Jedi, Jar Jar Binks, Jedis waving lightsabers around like cheerleader batons, the list goes on and on... So much potential wasted.
I think that's why everybody was so disappointed, because even subconciously people could sense that this prequel trilogy had the potential for true greatness, to be more epic and more tragic than the original trilogy, the backdrop is there. All it needed was a writer that knew what he was doing. Instead we got GL.
I wish that the PT could be remade at some point with improved characters and story but I suspect that one of the conditions that GL insisted on when he sold Lucasfilm to Disney is that the Prequel Trilogy can't be changed or remade, which would be a real shame.