About that demo:
The graphics are okay, I see you got them from existing games...
The particle effects look quite good, and fit a NES game.
The female and male voices are a cool feature, but the intonation could be better.
The gameplay didn't impress me. I expected it to have more fighting moves, such as punches, kicks, grabbing the enemy, etc.. And more special moves would be nice too. Also, it didn't feel like a fighting game, but more like a platformer. In this point I expected more.
The A.I. of the avarage enemies was very good, and metaknight's jumping also seem to have been difficult to program. But to tell the truth the fight against him was quite boring... he doesn't attack you often, he only keeps jumping and jumping all the time... I also expected more here.
The sounds and music were okay, but could be better too.
The mechanics seemed to be working well, but there is a bug in the collision.