This is a good idea. However, I don't see how you can really tell what AI is the best or the AI that just got lucky,
For example, Phil Ivey can get beat in a hand of poker by people way inferior to him.
The problem is also that there exist a lot of stuff about poker AI. I don't see how this would be different than say an AI competition about chess in the sense that there are thousands of AI on the web for chess.
A yu gi oh or magic the gathering type game might be better. I suppose you could make a type magic the gathering game that six people can play.