HuntrRose said:
I'd go older and say the Shichinin no samurai, Yojimbo, Sanjuro and most of the other films Akira Kurosawa made with Toshiro Mifune.
But can they be classified as "martial arts" movies?
Oh yeah, if you don't mind silly amounts of blood, then the Lone Wolf & Cub/Daigoro/Shogun Assassin thing isn't half bad. And while we're in Japan, Takeshi Kitano's take on the Zatoichi story was pretty decent, as well.
Other than that, the good ones have mostly been mentioned. Ip Man, Drunken Master 1 & 2, Enter the Dragon, Hero, House of Flying Daggers, Snake in Eagle's Shadow, Once upon a Time in China...
And while they're technically more historical war epics than martial arts flicks, I'd recommend Musa and Red Cliff, as well.