There are two videos on Youtube which, judging by the comments below them, seem to convince people of Bruce Lee's brilliance.
Both videos are excerpts from a single film, apparently shot at the 1967 Long Beach Tournament and available elsewhere on Youtube.
Surely any experienced fighter watching this would agree: Bruce's opponent here is absolutely terrible, and is a poor opponent against which to demonstrate one's abilities. He telegraphs every punch and kick loudly, not only by retracting his fists, but with unnecessary whole-body movement, often dropping both fists ridiculously low (to waist level) and his head as he moves in (see 2:22 for an example). This is true beginner stuff and no decent fighter would derive any pride from dismantling someone this poor. Many club fighters would have performed better against someone so incompetent. Someone may identify this fighter and point to his belt or reputational status, none of which alters the evidence contained in the footage.
Bruce's opponent maintains no defensive integrity and pursues Bruce stupidly, continuing to attack even though this is clearly ineffective. The 'ultra slow motion' section shows nothing but a rudimentary block (executed without any great skill) and also reveals a repeated failing of Bruce's. He displays virtually no lateral movement when under attack, which results in him being forced backwards and to be prevented from employing the counter strikes circular movement would enable.
This video seems constitutes no evidence that Bruce is a remarkable fighter (although his fist kick was decent). On the contrary, it suggests he is nowhere nearly as good as is so often claimed.
Anyone at home can replicate what Bruce did in this video. Admittedly the technique demonstrated bears almost no relationship to fighting skills, unless you think fights involve an opponent facing you with their arms at their sides, in an extremely weak stance.
Let's examine each punch.
In the first one against Joe Lewis (at the start of the video), Joe Lewis is standing square to Bruce, not in a fighting stance. The fact he was forced back has very little to do with power and a lot to do with balance. If you stand in front of someone with your feet square to them, it takes relatively little power to unbalance you and force you back. Additionally, Bruce's punch was less a punch than a push, which you can clearly see in the footage.
Bruce also employs a bit of deceptive stagecraft in the demonstration. Notice, that when he invites Lewis to punch the volunteer, the volunteer has no chair behind him. This allows him to backpedal freely and regain his balance. This is where Bruce plays his trick. Before demonstrating his punch, he positions the volunteer so the chair is behind him. The audience likely assumes this is for safety, but no, the chair actually increases the danger. The chair prevents the volunteer from backpedaling, and so he falls into it.
Also, if you pause the video, you will see the punch is nothing like a 'six-inch' punch (or the 'one-inch punch' for which he is lauded). His brings his fist back at least twelve inches (it looks like quite a bit more) and uses his whole body to punch through his opponent. There is absolutely nothing remarkable about the result. The fact the chair slid back so far is more to do with the participant's whole body weight falling into it after being unbalanced, and far less with the power of the punch. His display is consistent with claims he was interested in magic.
The trick is easily repeated. Try it at home with a friend (Use spotters, for safety reasons, and make sure the receiver is adequately protected both from the punch and the fall).
Yes, there is a lot of anecdotal evidence which seems to support claims as to Bruce Lee's virtuosity, but testimonials of this sort are worthy of considerable skepticism. It is not uncommon for myths to arise around certain historical figures, and for hyperbole to permeate apparently documentary accounts. We also know that testimony from friends and students and teachers (and others who may have had a personal or professional/reputationally dependent relationship with Lee) is far less reliable than independent testimony. Other analyses seem highly speculative; based upon vague accounts, opinions of 'experts' (such as famous fighters who never saw him fight), and upon tangentially relevant evidence such as Bruce's athleticism.
There is also footage - from the same tournament - of Lee performing sticky hand techniques whilst blindfolded. This is interesting and no doubt requires considerable skill, but there are again questions as to the competence of his opponent and to the utility of such skills in real combat.
I have reached no conclusion as to Lee's ability, but none of the footage I have seen reliably supports any claim he was a very good - let alone great - fighter.
Does any such evidence exist?
EDIT: Member Macaco Branco provides this link, analysing the same footage, including another sparring display Lee performed on the same occasion