"Crossover from Nintendo (Ex.: Mario, Sonic, Samus, Kirby, Cpt. Falcon)"
When did Nintendo take over SEGA?
Also, I like how SparkleYoshiFan is in your cast for the SMBX forums playable characters, but I'm not. I feel left out.

(Just kidding.)
Besides, your idea of having five characters from the forums fight against one villain trying to destroy the forums isn't new. We have two projects like that already; one is the Super Mario Community project that Natsu is making, the other is an episode where you play as Valtteri and have to defeat Kyasarin and DarkYoshi (I think).
About the poll, I prefer the original cast of Mario, Luigi, Peach, Toad and Link. Sometimes I add one or two Yoshis as playable characters, but I mainly play as Luigi, sometimes Mario.