Good effort
I liked the art and the backgrounds for the most part. sadly the engine, and Im sure you worked hard on it, just doesn't have enough to keep things fresh. on top of that the player is overpowered so the gameplay ends up broken. I got to the second boss without losing a life, just by holding down the A button and the right arrow.
not sure how you didn't catch that before releasing it. Also is there any real use for the jump button? these are simple things you must ask yourself before even starting the engine. its all gotta work on paper first.