Well, a lot of people are missing. Truthfully there have been so many action stars out there through the years that if you were to be fair, the list would be huge, and most would get one or two votes. Van Damme has had some good movies (and I don't think he was mentioned yet), then you of course have Carl Weathers, Mel Gibson, even Patrick "Roadhouse" Swayze (who also did "Steel Dawn"). Don "The Dragon" Wilson did how many of those direct to video "Bloodfist" movies? (someone must watch them). Then of course you have Lorenzo Lamas who did a couple of decent movies, and then held down the show "Renegade" for years. Don Johnson managed to hold down a role as a TV tough guy for years, Miami Vice, Nash Bridges, etc... he also got some regular movie roles as well.
If I had to pick a general "best" it would be Arnie, he's my enduring favorite.
Though admittedly if it comes down purely to martial arts movies I'd say "Enter The Dragon" is the one to beat, it is so far the best martial arts movie ever, and the one all other movies of the type strive to be. I'm not saying a better one can't be done, but to me this movie has never been knocked out of place as the best.