A good start...
You got some potential but you got a lot of room for improvement. First off, it was way too simple. Two characters on a basic non-moving background. What you should try is this, multiple layers. Sure all sprites are 2-d, but with more layers and detail, you can easily add the illusion of that third deminsion. Also try to avoid the repetition. Try your best to make each action a different position. Know what I mean?
The sprite fighting division on NewGrounds is a rough place to gain fame with artists like Alvin-Earthworm and Proxicide dominating it with amazing visual effects. So I suggest first, try using sprites that are uncommon but flexible, so its not just another Mario, Sonic, Street Fighter, Mortal Kombat, etc etc etc. Also don't be afraid to invest in higher quality effects. A well placed effect can seperate a punch from a huge blow.
Surely I have only said things you already knew but I just wanted to make sure you know. Good luck on future endeavors and follow these simple rules to vacuum up everyones 10's and 5's.