I thought about responding to this thread in detail, but it would be a long rant. Lots of people have summed up some of my problems with the prequels so I'll let those stand in place of my proposed responses.
Suffice to say, the Prequels had problems, major problems, and while the Originals weren't free of their own problems, they flowed much better and the story made sense.
I will expound on one thing though, people always say that there was some unrealistic expectation of what these prequels were supposed to be, I call that bogus. The Originals built up the story of a powerful Jedi who turned to the Dark side and hunted down and killed all of the Jedi. They made us believe that Vader was evil, and powerful and unmerciful. They gave us a sense of doom when he was near, and the only thing that could save him, was love for his own son. The Prequels were supposed to be about 'that' guy, and they weren't.
Anyway, I think the prequels fell short. I went in with the expectation of getting Star Wars movies, and I watched them and enjoyed them some. What I didn't get however was good Star Wars (which I think is a reasonable expectation since Lucas had 20 odd years to prepare and refine his story), and the more I compared them to the Originals, the worse they became.
Not because I'm nostalgic and only want to live in the past, but because I wanted Lucas to add something to the story, and these really didn't (other than a couple of cool planets, props to Timothy Zahn) space ships, and some neat lightsaber fights. They fell short of the epic that was the first movie, but they could have been so much more.