I understand not ranking Obi-Wan that much more highly than the likes Agen/Saesee/Kit; I'm not completely sure how I see it yet but I'm thinking I probably would rank him quite a bit above them but not drastically so, but it seems that on one end you have his far greater exposure leading people to believe he's leagues superior, but then on the other end you have people more deeply analysing the source material and concluding that he hasn't truthfully proven himself to be vastly superior.
But even if you think of him in the same light as the Kit/Agen/Saesee trio, being the absolute master of the style designed for defence, I cannot imagine that Sidious would be able to handle him quite as easily.