I don't think anyone here is going to argue with the idea that a person should not "enjoy" these movies. I "love" Howard the Duck even though it's an awful movie. The experience of the movie in no way has to reflect the material of the movie. I think the new Star Trek movie is a great example or even Avatar. I loved watching both movies and had a great time even though both movies have a rather abysmal screenplay attached to them. Again, the experience was separate from the material. This can be the case for the prequels, but I find it very hard to accept, nor can I after all the picking apart I have done, to call the prequels well written, well acted and well directed. I have talked to quite a few people on this movie and have seen quite a few reviews and examinations and most of the time everything comes down to the following areas
1) Yoda: In the OT Yoda was a theologian and philosopher. A very wise, very experienced and very powerful figure in the Star Wars universe, not because he was jumping around with a lightsaber, but because the character itself. In Empire Yoda gives a riveting speech on the Force that I use to this day to describe it. It's practically a homily on how the Force is there to help you, but you have to have faith in the Force, not in your skills as a Jedi, but in the Force itself as if the Force is beyond human comprehension but we allow ourselves to look past human logic and believe elements of the Force that are simply impossible for a human to understand; it can help us achieve the impossible. I'll get into more of this later. Yoda's character was intriguing, yet awestriking. Very much like a wise monk with an answer to any trouble that life throws at you. In the Prequels this is not the Yoda we see. Here Yoda fights. And he fights. And he says a few lines of wisdom but never anything that comes close to the one scene in Empire and his homily on the Force. Many times people point to the lines where Yoda says "Hate leads to anger..." as Yoda being philosophical again but these lines are pretty superficial. Anyone could have said that line, Obi Wan, Mace, any of the Jedi's on the council. Yoda saying them was Lucas's attempt to show us, "oh, he's wise too!". Sorry Lucas, but no one is buying it this time.
2) The Force: Like I said above, the Force in the OT was a spiritual essence and being, not a physical or material essence. It was painted as something that anyone could potentially tap but some were more drawn to it than others, kind of like some are drawn to be priests. They have a tendency towards the force that makes them more open to it. Han presented the agnostic side but Luke responded to it as if Han "could" believe in it, although tapping into it was never discussed. Another thing discussed in the OT was the dualistic approach to the Force. The Jedi's believed in order and discipline of the mind and that the Force was there if you purified the body so that it can be received in its fullest. The Sith believed in passion and emotion as a channeling power to the Force and that only through the more powerful emotional appetites does the human body access this essence. The evil of the Sith was presented as an effect of their tapping into this hate and wrath constantly. But Luke reminded Vader how to love again as if the person behind the evil, this Sith was once an innocent being that once felt love or compassion during his life. In the Prequels the Sith are not like this. There is no humanity behind the mask (although Palpatine never once showed positive emotion in the OT either) and worse off the Force was degraded to a physical reality, not a spiritual reality. A good powerful Jedi was not measured by their faith or wisdom, but by the number of midiclorians in their system. This would be like comparing two Christians and saying one of them is a better Christian because they have type B+ blood. The Prequels eject the wisdom of the force and replace it with choreography and numbers.
3) The Characters: This is easy. Watch Red Letter Media's review on The Phantom Menace and he performs an experiment. It's enough to prove the characters in the OT were 3 dimensional and the prequels characters were 2 dimensional, most of the time 1 dimensional, always acting towards a straight line and never wavering from it, but even worse not even showing life, simply just saying their lines. Nothing more needs to be said on it as Plinket said it the best by simply showing us the experiment.
Lucas DID ruin the Star Wars universe by throwing out the original idea of the Force, by ejecting the idea that characters can be 3 dimensional, something that has NEVER appeared since the curtain closed on Return of the Jedi and by taking character's we once knew and creating a brain dead origin story for them. Obi Wan went from a wise old hermit to some guy who fought in the Clone Wars. Anakin went from a dark soul who once loved but is consumed with hate to a whiny brat of a kid that complained all the time, the love story forced into the picture. Yoda was a wise, awestriking figure and was turned into the Jackie Chan of Jedis. Palpatine was a figure filled with so much hate and anger you kinda wondered how someone could fall so far and then you learned, oh.. it just happened. I'm a conniving political figure. *snap* now I am a raging, hate-filled dark figure. An article was released a while ago from Lucas's producing partner on the OT who in so many words stated that he left after making Empire because he wanted to make a movie while Lucas wanted to make money. This explains everything.
the OT represents a Star Wars that works. Everything is interesting and you want to delve more into this universe. With the Prequels the minute the curtain closed I forgot everything. I had no interest in pursuing any of the characters because I really didn't meet any characters. I didn't really care for anyone or want to explore anyone. Imagine reading the first Harry Potter book but start with Hagrid finding Harry, Harry entering school, show only the scenes that discuss the plot about the philosopher stone and jump right off the bat into the end, throwing out any form of characterization that moved the character's forward, not the plot. in the Prequels the plot was the only thing moving forward, the characters simply came along for the ride. In the OT, character's WERE the prime mover of the plot.