How did Anakin Skywalker become Darth Vader? What sent a promising young Jedi down the path of the Dark Side? That is the central question at the heart of the prequel trilogy. The question is answered fairly powerfully in Revenge of the Sith, which (like all the prequels) has its issues with some clunky execution but also has plenty of awesome stuff. At the end of the day it tells the story, completes the journey, and gets the job done, especially considering its need to engineer a predetermined outcome.
Anakin's tale is ultimately a tragedy, because he didn't intend to go to the Dark Side. He wasn't evil because he liked it or wanted power for its own sake, the way Darth Sidious clearly does. Anakin was manipulated into evil after a series of bad or blind choices and desperate moves. The battle between ostensible good and evil is grayer here than one might have expected. The opening crawl succinctly distills the complexity of the war itself: "There are heroes on both sides. Evil is everywhere." Sith continues the idea from Clones that the war is a complicated political situation, where being on either side is not to be on the side of angels. Indeed, since both sides have been engineered by Palpatine, there are only losers, except for Palpatine, who won't get his comeuppance for decades.
What's interesting is how Anakin finds himself backed into a corner until his only way out is the Dark Side, which corrupts him with the evil that will become Darth Vader only after he's started down its path. Much like when he foresaw his mother's death, he now foresees the (recently pregnant) Padme's death in childbirth. Determined to stop it, and because Palpatine is such a master of manipulation, Anakin is receptive to ideas he might not be otherwise. The scene where Palpatine explains the tale of Darth Plagueis the Wise — who could allegedly stop people from dying by using the Dark Side of the Force — is a haunting piece of storytelling that's a million miles from the terse exposition of The Phantom Menace. It might all be a lie (though it might not, given how Palpatine tells how it ended), but the point is it's exactly what Anakin needs to hear to be pointed in a direction that most benefits Palpatine's scheme to recruit his apprentice. This scene is what this movie is actually about, and what the entire trilogy has been building toward.
I still marvel at Palpatine's long game and how he's able to twist every development to his advantage. When the Jedi Council asks Anakin to spy on him, it's just the sort of thing Palpatine can sniff out and exploit, by raising questions in Anakin's mind about whose motives should be distrusted. It's a testament to Lucas' screenplay that it uses so many layers of motivation and pushes all the buttons in Anakin's character flaws — pride, impatience, fear, jealousy, misplaced loyalty — and then uses them to move Anakin along this path. Ultimately, once Anakin realizes Palpatine is the Sith Lord and turns him over to Mace Windu, Palpatine is still able to manipulate the situation until Anakin finds himself siding against Mace (who gets an adequately spectacular demise). Anakin's final turn to the Dark Side happens because he made the wrong choice and now thinks he has no other option but to commit.
The downside of all this is that it makes Anakin — and by extension Darth Vader — into a pawn whose identity was built on a series of personal failures and rapidly compounded bad decisions. And behind all that is Hayden Christiansen, whose performance isn't quite awful but also cannot be called good. The portrayal of Anakin is still too much of a young, whiny, jilted man who didn't get what he felt he deserved and was exploited as a result. Is that an interesting character arc? I would say so. Is it the one we wanted for Darth Vader? I'm not so sure.
That said, given the parameters I do think Christiansen could've been better than he was in this trilogy. He never owns the part — and merely seems to be playing it — and considering he's the central character, that's a major problem. His scenes with Padme, even here, don't work. Natalie Portman is a good actress, but you wouldn't know it from a lot of her work in this trilogy. This is a supposed to be a tragic love story we care about, but the performances never rise to the occasion to make it credible. I think this goes back to George Lucas and his apparent limitations as a director. He's a master visual storyteller but only mediocre when it comes to his actors.
And that's too bad, because Lucas has the material on his side this time. Alongside Anakin's fall, this is a dark and powerful story about the death of democracy, the rise of fascism, the pre-planned destruction of the Jedi with Order 66, and the triumph of evil. The moment when Palpatine dissolves the senate and forms the Empire (promising security) is met with applause, because people are so sick of the war. And later, when Yoda attempts to defeat the newly self-appointed Emperor, their fight appropriately takes place in the senate chamber, where they use the Force to hurl massive senate-seat pods at each other — literally destroying the instruments of the Republic's democracy. It makes for some truly epic, operatic drama.
As a sci-fi adventure, there's plenty here of course, including the showdown with the separatists and the droid army led by General Grievous, who is an intriguing creation blending creature with robot (I love the metallic cough) and at one point pulls out four lightsabers at once. The opening battle over Coruscant is massive in scale, and we later get to see Yoda overseeing the charge on the Wookie homeworld of Kashyyyk.
Of course, all of that pales in comparison to the final emotional showdown between Obi-Wan and Anakin amid the volcanoes of Mustafar. Again, epic and operatic. The whole trilogy has been leading up to this showdown, where Anakin's betrayal must be challenged in the most personal of confrontations. Setting this within a fiery hellscape is the only real choice. Ultimately, it's Anakin's overconfidence that ultimately leads him to lose. When we later see the horribly disfigured Anakin actually transformed into the Darth Vader of Episode IV, it's a potently horrifying picture. Even in this moment the Emperor twists the knife to seal Anakin's fate as Vader: When Vader asks about Padme, the Emperor lies and says Vader killed her. (Vader's "Nooooooo!" seems to be one of those things that divides fans and is often ridiculed, but for me it was an effectively operatic way of completing this story.)
The real reason for Padme's death is unfortunately quite inane. After she gives birth to Luke and Leia, she dies, not in childbirth or because of a medical reason, but because "she has lost the will to live." It's a real groaner of a moment — a lame excuse that betrays the script's gears turning to manufacture an outcome at all costs. I understand the reason why Padme had to die in service of Anakin's final arc, but couldn't Lucas have come up with a better way than this?
So it goes. Revenge of the Sith — the best of the prequels — falls short of greatness because of too many clunky moments like that. But this is a solid and satisfying conclusion to a flawed epic. My position (and it's just, like, my opinion, man) is that anyone who writes off the prequels as terrible isn't looking hard enough at what's there or is unwilling to balance the scales considering them as a whole. I've seen a lot of prequel derision in the weeks since the release of The Force Awakens, and to me it feels a bit like revisionist history. Greedo didn't actually shoot first.