Dooku was a must. So many posters/wallpapers prefer using Grievous and neglecting Dooku, but Dooku was more important to the plot of Anakin's downfall, and he was an actual Sith (in a movie called Revenge of the Sith). And he's Christopher Lee. Christopher Lee.
I love both trilogy finales (Return of the Jedi and Revenge of the Sith) the most of all the Star Wars films, though I love all the films pretty much equally, and depending on my mood of course. There's a sense of profound destiny, an inescapable conclusion in both the ascendancy of the Sith and the return of the Jedi that makes the end films of both trilogies so much...fun.
Looking back on the prequels, no pun intended, they seem to have crammed a lot more dialogue and story so hats off to the producers they did a good job. I do think revenge of the sith should have been a 2 part film like the last Harry potters.