You should really increase the framerate! I like to use about 26-28...also time your animation cycles better! Grab a stopwatch and try to see the keyframes in actions like walking and punching. See how many seconds it takes to throw a punch or take a step, then break down that time into frames...for example, if it takes me 1.5 seconds to take 2 steps, then that might translate into 40 frames for a walk cycle, with about half as many keyframes.
At least, that's the way I always understood it.
Also, most people are accustomed to moving in computer games using AWSD not arrow keys...
The basic attack for the dude kinda sucks, the range is really limited...I don't have volume so I can't attest to the SFX or tunes. I think this is a really great first effort! Could be a blast, with less choppy GFX, upgrades, equipments, smoother backgrounds, etc etc etc...
Good luck!