The prequels are too filled with stuff that "looks cool" and doesn't really fit the story. A great example of this is General Grevious. Why have this caracter? He just suddenly appears in Ep III, and is little more than a throwaway villian. Does he serve any purpose other than "wouldn't this make a great action figure!" He seems to do little for the story. If you insist on having Grevious, why not introduce him in II, or do something like have him actually be Maul, or something that ties him in to the rest of the story.
The jedi force powers also fit into this area. It looks cool to have a hyperactive jumping Yoda, and Superman-like Mace. Even if it doesn't fit, we'll explain it by saying that the Jedi in the OT were old(Obi-Wan, Yoda, Emperor), crippled (Vader), or untrained and didn't know what they were doing (Luke). The problem with this is that in the prequels, people like Yoda and Dooku were already really old and it didn't hurt them any, Grevious was crippled and still did great (I know, he isn't a real jedi, but still). And if Luke was untrained and not ready, then why the heck was Yoda and Obi-Wan determined for him to face down Vader? Did they want him to get killed?