Lol are you a troll? The irony here is that if I were to do as you say, I would come up with countless sources proving you wrong. Just by watching the films I know this is not the case, Sidious took out 3 Jedi Council members in a matter of seconds, and defeated the leader of the most powerful incarnation of the Jedi Order. By reading Darth Bane I learn that Sidious was not a traitor to the Sith ideals, and followed the Rule of Two - the pinnacle of dark side teaching.
how is that even a serious question? who and where does it say sidious was the most powerful sith? that notion is laughable and amateur. if you have done any amount of serious research you would know that sidious was extremely weak and a tratior to the sith ideals. also not to mention that the level of lightsaber mastery far outstripped these modern day jedi/sith. so to answer this question malgus would crush him like a bug with the force and carve sidious up like thanksgiving turkey. its no contest at all
Oh yeah and the 'level of lightsaber mastery' in the Old Republic era is in fact weaker than the Prequel Era. Makes sense as things tend to improve over time, rather than recede. The Jedi Order had experienced a Golden Age of peace, giving them plenty of time to become closer and closer to the Force and more and more powerful.
Its also ironic that people like you and others are whining about people pulling the canon card, and then being completely hyprocritcal by pulling the 'anti-canon' card and completely disregarding the entire star wars universe because you think 'canon sucks'. If you don't like the universe, go somewhere else.