Revan is a great character, but he's not even close to Sidious. That's nuts.
Sidious truly accomplished something that every true Sith, fake Sith, Dark Lord of the Sith, and Dark Jedi only dreamed of:
He ruled the galaxy and wiped out the Jedi.
In the end, it doesn't matter how he did it, only that he succeeded where every other Sith Lord failed. The Republic, which had survived for over 20,000 years, had withstood a Mandalorian invasion, Exar Kun, Revan, Malak, the second coming of the Star Forge, a Jedi Civil War, Darth Bane, and more was destroyed by the machinations of one man, Darth Sidious. I think that pretty much ends the debate.
If you actually need any more evidence:
-Sidious enslaved THE Chosen One by turning him into a Sith Lord. Revan was captured and enslaved by the Jedi Council.
-Sidious triumphed over Yoda, Mace Windu, Obi-Wan Kenobi, and Anakin Skywaylker, four of the greatest Jedi EVER. Revan couldn't defeat those schlucks Vrook, Vandar, and Bastila Shan.
-For his/her great tactical mind, Revan was lured into a trap and his ship boarded and basically taken over by a band of Jedi.
Would Revan defeat Sidious in an isolated duel? Quite possibly. There's a good chance that Revan's skill with a lightsaber + his/her force powers would trump Sidious' own immensely strong dark powers. Give both of them a small fleet and Revan would outmanuever Sidious. Give each a galaxy and Sidious would end up ruling them both.