Okay, I'll add my bit to the broth here:
(1) ONG BAK and ONG BAK 2
(2) friend got them on blu-ray on sale over at Best Buy; hadn't seen ONG BAK in a while and wanted to see it again (to see if it came out better than I remembered) and heard all sorts of crazy things about OB2.
(3) ONG BAK is pretty decent! Story is pretty typical for martial arts movie (main dude - Tony Jaa - lives in poor town, whose sankara.. er, buddha head is stolen. He must go into the Big City, find former friend and get him to help find said stolen Buddha head, which leads him to a crime kingpin who has been stealing and selling Thailand artifacts. Needless to say, ass-kicking ensues). The first time I saw it, it seemed that EVERY big scene with Tony Jaa doing some amazing stunt work did the POLICE STORY triple-take.. yet for some reason, I didn't mind it this time.
ONG BAK 2 though.. HOLY CRAP! The english dub is quite silly, as the Monty Python folks would say (yet somehow it still fits), but the movie is either crazy fantastic or crazy stupid, all depending on how you take your martial arts films. I would say this is the best film I've seen when it comes to really showing off various martial arts in action, where the fighting is deadly serious, fast and BRUTAL! Jesus Christ on a tap-dancing pogo stick is this movie brutal (and not in a SAW way)... you have to watch it just for the things Tony Jaa does. Plotwise it is again typically simplistic, but again, if you are a fan of martial arts movies you pretty much expect this.
PS: bit of trivia: apparently, Tony Jaa fired the director halfway through filming and took over the director chair himself... and then about 3 weeks later, Tony disappears! About 3 weeks after that, some of the crew found him in some remote Buddhist temple deep in the Thai jungle and had to be dragged back to finish the movie.
(4) overall, at least for me, I would give both about a good 7-8/10.