Originally posted by S_W_LeGenD
Fapping to The Old Republic MMO
#1:
The Emperor, having gone out of his way to keep Vader alive, took an alternative viewpoint. Though it was true to say that he had not bargained for an apprentice that was "more machine than man", Palpatine was of the opinion that most of the limitations on Vader's potential power were not physical but psychological. He believed that, were Vader to fully confront his choices completely shake himself out of his despair, he would have been able to reawaken the incredible power of the Chosen One within him. To an extent, this was true: once he got used to his armor and re-tooled his fighting style, Vader became an incredibly powerful Sith Lord. However, he would always be haunted to varying degrees by the choices he had made, even to the point of what amounted to temporary insanity during his mission to Atoa. Thus, while Vader made progress in this regard, he was never fully able to accept who and what he had become, and therefore never fulfilled his potential. Sidious would ultimately come to realize that Vader would never be the apprentice he longed for. He would try to replace him on at least two occasions with more powerful Force-sensitives, Galen Marek and Luke Skywalker. The Prophets of the Dark Side also saw Vader as too much of a Jedi to truly embrace the Dark side.
#2: They demonstrated less power and overall capabilities in combat, despite their "neat Force powers". You can't just say they're more powerful but simply lack the showings to prove it. Let's not forget Mace Windu crushing General Grevious' chest, or Yoda TKing Droid Capital ships practically as large as Star Destroyers with ease and precision. At least we can assume Yoda and Mace Windu are eons ahead of other Jedi, only faintly matched by the likes of Obi-Wan or Qui Gon Jinn, and more closely matched yet still far beyond the likes of Count Dooku and Darth Vader...and surpassed by Sidious.
#3: Yes he was. As for Force powers his Force speed and TK allowed him to destroy an entire army of Super Battle Droids and their super weapon pretty much on his own, at parts of that battle he was unarmed. Ian (the actor who played Sidious) explains that Mace Windu fights hundreds of times faster than other Jedi in the Making of Star Wars EP III.
And don't let me start on Yoda. He was canonically stated in the ROTS novelization as the most powerful Jedi the order had ever known. I hope you can understand straight canon statements and the weight they hold.
#4: Yes he does, 😛
#5: So you're a canon source now? Read Gideon's Darkness Beyond Darkness: I am not making my canon statements up, and at least I'm giving sources (ROTS novel for both Palpatine and Yoda). To compound Gideon's three examples of Palpatine being the strongest Sith ever in canon statements, Maul stated it as well in CW during the 4th Season). The only other time a statement like this was made was on the plot summary on the back of the Darth Bane: Dynasty of Evil novel...which was not a canon statement, but stated that Zannah and Bane were the strongest Sith Lords in history.
#6: The Emperor was conjuring a Force storm during the duel, and purposefully lost (as he effortlessly disarmed Luke in a duel mere hours earlier, that loss could be nothing more than intentional, even with Leia and her child's help through Force valor/Battle meditation). After the duel Luke, his sister, and her unborn child used Force Light to turn the Emperor's Force storm on him...which had nothing to do with his lack of power. it was a variable Sidious hadn't considered, and one he wasn't prepared for, like losing a duel with his apprentice Luke.
#7: Vaapad didn't save Windu, an opportune shatterpoint did when Windu and the Emperor's stamina began to fade. The Emperor could have easily overpowered Windu without three other Jedi Masters, one of them powerful enough to defeat General Grevious (Kit Fisto, Clone Wars season 1), that further debilitated his stamina, which still was equal to the young Windu's afterward. And then in Empire's End, after his only good Clone body had been destroyed by his Dark Side Wormhole, the Emperor's pathetically weak physical form again proved unable to wield the necessary dark side energy to stand against Luke (stronger than Satele and Revan at this point, practically Legacy of the Force level) and his Jedi.
Point being the Force can only do so much when you're old an bridle like Palpatine, and outnumbered. It was not on equal terms, if Windu had been alone he would have died before Sidious' power went plateau as it did when he was aided by Kit and the other two Masters. Remember it took him a few more seconds to kill Kit, whereas the first masters died instantly, then it took him several minutes before he and his last assailant expended their last reserves.
#8: Because they both realized they were no match for the strongest Sith Lord in the mythos. In both novelizations this is stated.