OK, my kids and I just finished a massive Star Wars rewatch which entailed all six films, the Gendy Clone Wars, and the entire Clone Wars series, including the film and Season 6, watching all in chronological order. The Clone Wars did have an impact on the prequel era. Like most, I prefered Matt Lanter's portrayal of Anakin.
Since Episodes I & II come first, the Clone Wars really doesn't come in effect until Episode III. And I noticed the following.
First off, while watching Episode III, it really felt like these characters went through a lot during this war. It did feel like this was the summation of what happened in Clone Wars.
It had an effect on Order 66, since before, these characters were more silent background extras that are killed. Now there was a bit more to it. Sasee Tinn and Agen Kolar (or is the other one?) weren't really fleshed out in the series, so the effect is minimal. Kit Fisto is enjoyable in the series, but his death is still ridiculously quick that it is kind of sad to see no fight in him. Ki-Adi Mundi benefits from more characterization, but near the end of Clone Wars, I lose a little bit of sympathy for him. He's the one who seems to want to throw Asoka under the bus and quick to think Yoda(!) was under the influence of the Dark Side. Ayla Secura got some recognition, but it was early in the series, so the tie wasn't that strong.
The one who you feel more for was Plo Koon. Watching him get shot down after following him in the show, particularly his ties with Asoka, makes the scene more effective.
As for Anakin, aside from the initial disconnect of Hayden's performance (and the Genndy's Anakin) following Matt's performance, Clone Wars really helps after Anakin gets on Coruscant after the opening. After watching Clone Wars Anakin, ROTS Anakin's actions, reactions, and motivations seem better. You can understand his desire for order and handling things efficiently, his lack of faith in the Jedi Order and by extension, Obi-Wan, and his (very strong) devotion to Padme. Yes, the youngling thing is still a bit much, but his turn feels better. Also, when he meets up with Padme on Mustafar, the way each plays it does feel like a natural extension of their characters in Clone Wars.
The Clone Wars also gives a big time boost to the Anakin and Obi-Wan duel. This is felt particularly at the beginning of the duel, just as it starts. It feels like a punch to the gut. And both reactions at the end of the duel nicely match how it would have been played by their Clone Wars counterparts.
So, short answer, yes, watching the saga with Clone Wars does help punch up Revenge of the Sith, particularly the characterization of Anakin. I recommend it to any Star Wars fan (with some time on their hands!).
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