I liked Black Mask for what it was -- an over-the-top superhero adventure. TONS of fight scenes and Jet's as charismatic as ever.
MoonRaven -- if you like Jet Li, you should check out these flicks if you haven't already:
Fist of Legend
Once Upon a Time in China
Dr. Wai in the Scripture with No Words
Fong Sai Yuk 1 & 2
Once Upon a Time in China and America
Hit Man (aka Contract Killer)
Bodyguard from Beijing
The Shao Lin Temple
My Father is a Hero
Tai Chi Master
Last Hero in China -- actually not all that good a movie but totally worth it to see Jet performing chicken kung fu. Yes, that's right, chicken kung fu -- he moves around like a chicken, poking his head and flapping his arms
Lethal Weapon 4 -- also not all that great a flick but Jet's definitely the best thing about it. The final dock fight where he takes on Glover and Gibson is bad-ass. Director Richard Donner said he was so fast they had to ask him to slow down because the camera wasn't picking up all his movements; Gibson said he was so fast he had to actually memorize which direction Li's blows were coming from and hope he could react in time to sell each punch.
What I like so much about Jet Li is that he's a martial arts phenom; the guy was born to be a martial artist and was a genuine expert long before he became an actor.