While Darth Sidious did change the Sith alot, it wasnt as permanent as Bane. Banes ideas of the rule of two lasted for over a thousand years, and without them Sidious never would have ruled. Sidious created the rule of One, and changed the Sith into galactic rulers, but this lasted far shorter than Bane's changes.
While Sidious is often credited as the Sith Lord who destroyed the Jedi Order, the plan goes far back into ancient galactic history. Darth Bane created the Sith Order that was present at the time of Order 66. Although Sidious did destroy the Jedi, he could not have done this without Bane's accomplishments.
Darth Sidious was the face of the Sith, and the head of Order 66. He defeated the Jedi, one of the most powerful orders (besides themselves). Sidious made the Sith into galactic lords! And frankly, barely anybody knows about Darth Bane. Sidious is one of the three most known Sith people (aster Vader and Palpatine).