I think Jacki Chan has some of the most interesting fight scenes ever made, but I don't know if I could say he has any of the best.
One thing I didn't like about Legend of the Drunken Master is that the last fight was very similar to the one he had in Drunken Master against "Thunder Leg". Though, the quality of the fight is much better, the style is too similar I thought.
As for Ong Bak it does have some good scenes:
I don't know if I could really pick a clear favorite any scene, there are tons of good ones.