Mace says that Kenobi is THE master of Soresu in the ROTS novel so as far as that time period goes, ion Mace is saying that about you then yeah, you're the best at that style
Hi yes just heard it by word of mouth have to find the channel you know that Star Wars channel on YouTube called Star Wars theory and Stupendous wave it was one of them ..
Here it is this guy does good stuff he mentions it from the start In the above link with regard to yoda thinking mace will surpass him .. not sure how true or accurate he is though .. but his stuff is pretty good ..
You know, the real problem is that the whole "lightsaber forms" detail is so particular and overcomplicated that most authors have stayed away from it, choosing instead to just claim that a certain duelist is "skilled" with a lightsaber. Now, since Soresu is based entirely on defense, it's easier to find examples of people who've been said to particularly good at defending themselves, but only major sources like the ROtS novelization have bothered to actually point out that Kenobi is one of the greatest masters of the Soresu form.
So, it's likely that if we're going by authorial intent, someone like Sidious or Yoda or Luke, or even Revan is probably better than Kenobi at defense, by virtue of being more skilled in general. But when it comes to sources verfying practicioners of Soresu, then Kenobi was the master of his time, and considering the Prequel Era was kind of the high point of the jedi in Legends, pretty much of all time.