Jackie Chan wasn't as good a fighter as Bruce, but I don't think that's the argument. His movie fights are better imo - they're so fast, intricate, funny, and so extremely well-choreographed.
Bruce's fights were awesome, it's something else entirely to marvel at the sheer speed, strength and technique of the man. Jackie can't match what he did, but he found a way to step up the entertainment in another way entirely. Injecting physical comedy, slapstick almost, into the combat, and his use of props and environment in the fights is incredible. I could watch Jackie Chan fights for hours on end.
Police Story 2 playground fight http://youtube.com/watch?v=AaQGvKjUycI
Police Story mall fight http://youtube.com/watch?v=DvWNIIEovvU
Wheels on Meals, Benny Urquidez fight http://youtube.com/watch?v=zhXwPQU1iNo
Project A, bar brawl fight http://youtube.com/watch?v=K8ks49ybos8