Not too shabby.
It was pretty good for your first time, but I have some suggestions for the next:
- Longer. It was wayyy too short. I would've like a longer fight scene with the boss and the enemies put up more of a fight.
- Music +SFX. i know you used SFX but try to use a greater variety. Like, 3 different punching sounds for example.
- Bits. Try to match the bits of your sprites. That juggernaut character looked so out of place between those characters with fewer bits.
Try to match them so it looks like an actualy in game cinema or something
- No numbers in intro. You might aswell used the word "one" insetad of the number. It makes it look kinda...noobish.
Anyway, I think you can go a long way. Keep practicing.