First off, The engine you used for this is the Stencyl engine which in the past other game makers essentially copied, modified the levels a little bit and called it their own. You at least modified the sprites and gave it a basic storyline.
Secondly, A complete lack of sound made the game dull. Even jump sound effects would have been nice.
Lastly, the difficulty and plot. There wasn't any. The character's hit box is so big that it's really difficult to fall down holes, there's no enemies and I didn't care about the plot.
Seeing as how it's your first game, I'd suggest learning more about actual game design, plot and even working on character design.
Good luck!