Nicely done
Overall, it was pretty good. I like the scratchy graphics, everything went well toghether. As in, the graphic style was consisten from character to character, and even the background. (It kind of reminded me of Earthworm Jim in a way...)
It moves kinda slow, though... I didn't notice any difference in speed between High and Low quality, so it wasn't that. If you're using some sort of frame-delay system in your code, I would shorten the delay a tad. The asteroid moved especially slow, considering they're supposed to be falling out of space at a rate of 24 feet per second, per second. (The slowness might actually be my computer, but I don't really know... it just seemed like it wasn't because I've played other Final Fight style flash games that were way more graphic intensive that ran much faster.)
As far as recommendations go... Have more stuff to interact with on the screen. Different objects to throw, maybe club upgrades. And graphically, I think it would be cool if there were craters when the asteroids hit (maybe a little vertical screen jolt, like it's shaking the ground? Also, the asteroids should probably be flaming red-hot for at least a few seconds. You'd have to let them cool off before you could pick them up and throw them. If anything touched them, it would probably catch fire!). You'll need bosses, of course.
I think the club powering up for a critical hit is a nice touch... and the music wasn't too bad, or annoying, even for such a small loop. Kind of reminded me of Tom Waits. Overall nicely done.