First of all, all your speculation about Plagueis is still completely unproven, including his creation of Anakin Skywalker (which is just a wild theory). I've even heard rumors that Sidious created Skywalker, so let's not base our discussion on hearsay.
It shouldn't be based on force power alone. Anakin Skywalker possessed way more force power than Darth Sidious or Darth Plagueis and that's a fact. He was a being of "pure force" but yet he chose to squander it all as a cyborg apprentice. Accomplishments are way more important than force power because force power means nothing if you don't do anything with it.
Other types of "power" include: Military, Financial, and most important of all: Political.
Eradicating the Jedi Order is the one and only goal of the Sith and Palpatine is the only Sith lord who has ever done it all by himself. Not only that but he did it basically by pressing a button. The genius it took to do that is the crowning achievement of all Sith history. He did something with mere words that it took other Sith lords huge wars and several years to accomplish. He wasn't a triumvirate or a brotherhood; he was just one man whose influence extended over the entire galaxy (not just his own little Sith Empire alongside the Republic) for many years (way more than just the Empire years). So no, no Sith lord has "accomplished more" according to me.
Of course I'm not very familiar with Star Wars canon to begin with, so answer me this: Is there another Sith lord who destroyed not only the Jedi Order but the Republic all by himself and all in the span of a couple of days at most?
Might I also remind you that Darth Sidious ruled the very first galaxy-wide empire? So even if he didn't rule it for very long, he was ruling the entire galaxy. Sure other Sith lords have ruled little kingdoms for longer, but none of them ruled the entire galaxy until Sidious. Even Darth Krayt only ruled the galaxy for 8 years and he inherited what he got from Sidious's original empire.
What's even more spectacular is that the Republic had lasted for over 25,000 years when Darth Sidious destroyed it.
If we accept the full EU (including his resurrection), his accomplishments, length of rule, and after-death legacy continue to pile up. Right now, do you know how many confirmed canon accomplishments Darth Plagueis has? As far as I know, 0.
Last edited by Klw; 05-27-2011 at 04:19 AM.