Hey not bad.
For a first sprite film there could be a lot of improvment. I feel great potential in your movie. But! I feel as if it was connected to Super Mario Bros Z in ways. I suggest a different idea. One only having to do with either Mario, or Sonic.
Although sprite movies don't really scream talent, when done right they can be the shit. (Good)
Fluent well ploted sprite animations are what get the score. Slideshows isn't that impressive. I would love to see full motion from you. Instead of having them in one position going to the next. Have them going frame-by-frame. It might be a bit of work, but it pays off in the end.
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The beginning music... Well, I would just have to say it's not the best choice. It really doesn't match the flash much. A simple little beat for the title screen is always a good idea.
Also the text should be improved.
It was short, and that's what you should focus on most. Making a longer video would help out dearly.
For right now that's all I can advise. But if you would like to know more, don't hesitate to PM me. I am always glad to help anyone in need of anything.