Not Bad, but needs work
This is not bad for a rough draft, but several parts of your flash need improvement. First, the speed of the dialogue was WAY TOO FAST!!! Slow down the speed of the dialogue so that the viewers can read the text with ease. I had to view the flash twice to understand what the characters were saying to one another. Second, the story is not very entertaining. Work on creating a better story, one filled with a more intriguing plot, plot twists, more action, and more character development (don't just say "I'm Samus. I killed Mario. I want to rule Nintendo Land." Develop the characters a little more.). Third, work on improving the style of your flash animation. Don't just use the same NES attacks from the original games, invent some individualized character attacks of your own. Fourth, create different musical themes for different scenes of the flash. Don't just use a single musical theme for the duration of the entire flash, create music that matches the scenes of the flash and character themes for each character you place in your flash (think about Chrono Trigger). Fifth, create some witty jokes to improve the humor of your flash. Don't just make Mega Man fall on Mario, create interesting dialogue between the characters and get a few laughs in here and there. And finally, work on putting different scenes in your flash besides the ones that are already in the video games of the respected characters (I noticed that you included Piccolo from Dragon Ball Z in your flash and you added a scene from Dragon Ball Z Budokai 2 for the SNES, I think). The more scenes you put in your flash, the more complex the flash will become and the more enjoyable your flash will be in the eyes of your fans. I don't know much about creating flash animation since I am not a flash artist, but I have seen many good flash animations here on newgrounds and I believe if you listen to the suggestions that I have made, your flash will definitely improve and so will your ratings.