To start with, I would give the plot of my films to a moderately intelligent five-year-old. Any flaws that he could detect would be immediately corrected.
The problem is that the films -- other than Star Wars -- all turn on an idiot plot. The only way that these events can occur is if the entire universe of characters is populated by idiots. (One might argue that Grand Moff Tarkin also failed the idiot test by letting the Death Star get blown up, but I'm willing to make some allowances.)
Don't believe me? The whole magilla starts to go down the tubes in The Empire Strikes Back. Obi-wan says to Yoda, "That boy was our last hope." Yoda replies, "No, there is another." And Obi-wan ought to know that, seeing as he was there when "that boy" and "another" were born. But who knows? Maybe being a ghost plays hob with your memory. Or maybe Obi-wan is just an idiot.
God knows that Darth Vader is an idiot. He knows that his wife was pregnant. Does he ever go to try to find his children? While it might be hard to figure out that twin Leia existed, looking in the stupidest possible place to hide a Skywalker baby would seem obvious. Especially given that Obi-wan is an idiot. Except that Darth's an idiot too. The Emperor too, for that matter.
Of course, the Emperor is saved by the fact that Mace Windu is an idiot. Otherwise, he might have showed up with sufficient force that he would have succeeded in arresting or killing Palpatine. "Hey, Mace, the most powerful man in the Republic is secretly a Sith Lord and you never noticed." Stupid! Stupid! Stupid! Of course, Mace also practiced dumping on Anakin, apparently for the sheer joy of it. God forbid we might be reasonable with the "Chosen One" rather than helping fertilize the field for Palpatine. But that's what you have to expect when the head of the Jedi Council is an idiot.
Anakin's an idiot too and I'd be tempted to blame that on hormones if there were any chemistry between him and Padme. Of course, Padme's an idiot and a cradle-robber to boot, but apparently intelligence isn't a requirement to be an Imperial Senator. But I'm talking about Idiot Anakin now, the one who kills all the Jedi "younglings". You'd think he might argue with Palpatine that the kids are a resource, but that would require that he not be an idiot.
Note how nicely we can drain all the emotion out of the line too! "He killed the younglings!" vs. "He killed the children!" Guess which one rolls off the tongue as you try to deliver it. Guess which one doesn't.
(It's sad when Gretchen and I plot better and write better dialogue than this. It really is.)
Then there's Idiot Yoda who decides for no apparent reason that he needs to go attack the Emperor with no backup. Great plan, Yoda. (It might just be possible to justify this stupidity with a line about Palpatine being obviously weakened by Mace's attack. Maybe.)
I'm also impressed by the way that Palpatine has managed to insert "Frag the Jedi" teams everywhere that the Jedi are stationed -- even more impressed that none of the other stormtroopers rebelled against this. Hey, and even more impressed that none of the Jedi noticed that they might need to worry about the men surrounding them, including Commander Cody (and the Lost Planet Rangers).
Oh, and let's not forget how "good-guy" Senator Organa thoughtfully has the arguably sentient C3PO mind-wiped at the end of the film. Boy, it's hard to tell the good guys from the bad guys.
But the singularly most impressive failure to read the Evil Overlord Handbook goes to Obi-wan for not making sure that Anakin was dead, dead, dead before walking off. Heck, he might even have given the coup de grace to a defeated foe that he had regarded as a brother, if he wasn't an idiot. It's not hard to write around this. Anakin might have been swept away on debris in a lava flow as C3PO called Obi-wan back to the ship to tend to Padme. At least then, Obi-wan wouldn't have had to be an idiot for the plot to work.
Technically, Revenge of the Sith is beautiful. It even has occasional useful moments.
But the characters have to be idiots for this plot to work.
And that's a damned shame.