Jim Kelly was in a number of other movies besides Enter the Dragon. In fact, one of the things I hate about EtD (and there are more than a few) is that they killed his character without giving him enough screen time, and let the white guy who obviously had about 4 days kung fu experience in his life be a hero and co-star with Lee.
I vote for the guy who was in Thundering Mantis and a bunch of others, but I forget his name (Fu Sheng?). I'm not saying he was the best...he was a movie kung fu guy, like most of them, not a real kung fu guy. But that movie was so great. "The kid, the kid...! They killed the kid..." and he goes insane at the end and starts eating people. Awesome.