Have I seen this before?
Actually, putting the plot in the future, after Mario and Bowser are gone saves your movie from being a rip-off of the other guys' films... sort of. Your style is generally the same as their's, however, which makes you seem like such a copycat.
Suggestions: Try going easy on the music and implementing some more sound effects. Or use some real Mario music, for a change. Yes, you might think that the original Mario music is not "dark" enough, but if you get creative with it, I'm sure you could fit some old Mario tunes into your films. If you count all the Mario games in existence, you've got some two or three-hundred tunes to choose from. Trying to remember a particularly dark one? Try the 'castle' music from Super Mario World.
If you do try some using Mario music, consider using it mostly in the background. Dark Mario films so far have been too much like silently reading an illustrated book while playing some overly dramatic music as a background to the reading. Real movies are generally not like that. Real movies try to draw us in through dialogue, acting, special effects, etc. Experiment with some of these thinigs for added spice.