Bringing back Vader makes no sense since he reverted to being Anakin once again just before he died. :P Granted, I didn't think the prequels were that bad. I honestly like "Revenge of the Sith" more than "Return of the Jedi." There's nothing fundamentally wrong with the basic story, which is what has always been what's at the heart of the SW saga for me anyway.
I do agree that bringing Vader back is a stupid idea. It cheapens his character arc, and would be nothing more than a cash grab over art. But then again, the prequels were all cash grab over art, so it won't be anything new to this franchise. As for ROTS being better than ROTJ, going to have to agree to disagree with that one. Yes, ROTJ had Ewoks and other problems, but Luke's near-turning to the dark side was better done and more emotional than Anakin turning into Vader, in my opinion. And of course, there's the whole Leia in the metal bikini scene, so that alone trumps anything in ROTS. As for my overall opinion of the prequels, just look to the Red Letter Media reviews of them. Lucas clearly had no idea what he was doing and if it hadn't been for brand name, those movies should have bombed.