In BJJ, he's pretty much everything he and everyone ever said he was. I honestly get weirded out by some of the stories I hear about how good he was, by very reputable sources. Jean Jacques Machado and
MMA is very debatable. You'll find two major schools of thought on it. Which is either he was an absolute phenom and would have murdered everyone up until around 2000, or that he was never any good and only fought cans.
Like most things, the truth lies somewhere in the middle I believe. He was in all likelihood the best fighter in the world for a period of time. Not many people can say that. However, the sport was in its infancy, and by around 1997, there's a lot of serious challengers that would have given him problems. Some have already been said in this thread. Bas, Ruas, Coleman, ect.
In all fairness to Rickson though, by the late 90's, he was entering his 40's.
It isn't really a cut and dry situation imo.