Ong Bak is VERY cheezy, like low budget early Jakie Chan cheese. I've had that one for over a year. The fighting is excellent, but the rest of the movie is, well, bad. The chase scenes are very Jackie Chan-esque. There were DEFINITELY wires used in some of the scenes in Ong Bak, but far fewer than most and pretty well done. I liked Fist of Legend better. Sorry, but it isn't the same genre as Hero, which is basically a drama, while Ong Bak is an action movie, so I wouldn't compare the two. In terms of cinematography too, Hero is in another league comparatively.
If you haven't seen Unleashed, give this one a watch when it comes out too. There are a few good fight scenes in it as well, the first one in particular.