I'd say yeah he was, the only real other notable users I can think of are Kun , Bastila and Satele Shan, but their feats or training don't seem to match up to his own. I can't really think of any other users.
He may well be the best, yeah. Of course, being master of every weapon and every style, I wouldn't be surprised if Sidious could best him with a saberstaff. He detests the things, though, so I wouldn't count him as a user even if he could do it.