Actually... there are some flaws in your post. Well for starters, Geno DOES have a decent shot. Why? Well, you tell me, whats the importance of a poll? You're so sure that Ridley has a better chance and yet Geno and Ridley scored the same on the official polls. Also, as I always say, if there is a more deserving third party character than Geno, then that character should have scored as high, if not higher than Geno on the official polls. We don't make the polls up, its solid evidence that Geno is popular. We can't change that fact.
Moving on.. now let me ask you this.. if Square Enix created Geno as a Mario character, to star in a Mario game and to only be a part of Mario games, how does that make him any less deserving than Mega Man or any other third party character? Geno is a Nintendo character with a Square Enix logo. The only thing thats keeping him held back is his copyrights belonging to Square Enix. You do understand that Rare created most of the Donkey Kong games and even though Nintendo completely owns the rights to Donkey Kong etc, they STILL have to credit Rare for their work. It wouldn't be surprising if thats all Nintendo had to do with Geno is just credit Square Enix and be done with it. I mean, what are they going to say? They created Geno for Nintendo and therefore Nintendo should have some rights to do what they want with Geno. You can't just go around and say "here I made this for you, but I want to own it", that wouldn't make any sense. That isn't to be confused with Nintendo owning the rights to Geno, but having partial custody of his rights.
Also, are you aware that Super Mario RPG is coming to the Wii VC? It isn't a "fluke" or a coincidence. Its a popular game and obviously Square Enix is all right with Nintendo releasing it on the VC. So what would make Square Enix say no to Nintendo if they want Geno in Brawl?
I've brought this point up MANY times before, the composer of Super Mario RPG and Mario and Luigi Superstar Saga is a confirmed composer for Brawl. Although her works is simply listed as Kingdom Hearts, it is safe to assume that Sora will not be in Brawl (this is a different argument all together). So if you notice, you don't see a single person that is representing Sonic's music that is confirmed on the composers page, but yet we know there will be a Sonic song.
So between Geno being one of the most requested characters, Sakurai adding random tidbits of information in his journal when he could have easily talked about other characters (this shows he is interested in Geno.. he probably never thought of adding him until now), Super Mario RPG coming to the Wii VC (Sakurai mentioned a small bit about how Kid Icarus is playable on the Wii VC..), the composer of both games that Geno is in is a confirmed artist in Brawl and last but not least, Geno can get by without stealing a third party slot.
So you do the math, are his chances really THAT low?