Bruce was a dedicated martial artist who was a student of all styles. On top of that he was a physical freak of nature. Insanely fast, crazy training regiment, shredded beyond all belief, ect. He was wise and mentally ahead of his time for martial arts...but there are a lot of unknowns as well.
No one really knows how good Bruce really was. He was an actor, not a pro fighter. Most of his feats are through word of mouth. His actually fighting prowess will never be known. Maybe all rumors were true. Maybe his charisma lead people to be mesmerized by his displays. Anyone who makes a definate claim either way is full of shit. None of us could possibly know.
I don't think it really matters tho. Bruce was and is to this day one of the greatest symbols of martial arts we've ever seen. The attention he brought to martial arts in the west inspired countless people to study martial arts.
Regardless of his actual skill, he did great things for martial arts as a whole