Last 3 films added some really valuable content to the backgrounds of Darth Vader, The Emperor (The Sith Lord Darth Sidious), Obiwan Kenobi. They gave the first 3 films some deeper meaning.
The Emperor (Sith Lord Darth Sidious) or Chancellor Palpatine:
The cool conspiring villain!
I was especially fascinated to see the massacre of the Jedi masters by the clone army, initiated by Chancellor Palpatine. How he had planned it all from the beginning; converting the old Jedis to the dark side, planning a clone army, (which is much easier to control & manipulate) and rising to political power, destroying the Jedi order. Brilliant conspiracy. He plays with the Federation and with Anakin Skywalker like puppets! He lets Anakin rise in power and confidence, cuts off his hand in duel with the help of his apprentice
Count Dooku, a former Jedi master. Then he lets Anakin kill Dooku in another combat, pushing him over to the dark side by encouraging his anger and desire for revenge. Finally when Jedi master Mace Windu almost kills Palpatine in duel, Anakin intervenes and helps him to kill Mace, thereby sealing his fate as a Sith. Anakin can no longer remain a Jedi, as he is now a traitor. Palpatine converts Anakin into a Sith Lord and takes him as his apprentice then and there, leaving him not a chance to repair the damage. He then orders Anakin to kill all young Jedi students and the weak links to the Sith chain. Without giving the Jedi any time to recover, he initiates a secret code
Order 66, which triggers the clone army to eliminate all members of the Jedi order by surprise. Publicly he vilifies the Jedi and claims total power from the hands of the Federation. You will find all this in Star Wars Episode III:
Revenge of the Sith. The Great Jedi Purge.
But there is a serious flaw in the film. They devoted very little time to build up the character of Jedi Mace Windu. They should have, for the story behind him is brilliant. He developed Vaapad and was the best lighsaber duelist ever. Also, there should have been more substance on Palpatine's dark side. The film-makers spent all the time on the sticky love affair between Anakin and Padme Amedala. Or they wasted precious resources building funny side-kick alien characters.
Finally Anna, I was not talking entirely about the 6 movies. I was also referring to the fabulous buildup of Jedi-Sith information written by novelists like
Drew Karpyshyn who contributed very interesting details about Darth Bane and the Sith order. Also works like
Jedi vs Sith have added new dimensions to the Starwars concept. The movies are but a narrow slice of the Starwars world, the tip of the iceberg.