Dantedemonslayr, that sounds so very phallic.
The truth of the matter is that it doesn't matter whether or not Cloud is more popular than Squall or any other FF character, because he is just that; a Final Fantasy Character. And thus, by definition, NOT a Nintendo character.
This is where everyone inevitably brings up Snake, and the fact that he is not owned by Nintendo. Additionally this will insight the constant bickering over what standard Nintendo is going to use for including third party characters. The answer? None.
The reason Snake was in the game is because the makers of Snake pushed for him to be in the game. Such altruism, which profits the makers of Snake virtually nothing aside from their own personal happy feelings, you will possibly see once more in your lifetime before you die.
Squaresoft will not push for Cloud's inclusion in Brawl, and Nintendo isn't going to pay through the anus to use a character that will improve the popularity of an already best selling series only marginally at best. Likewise, it would benefit Squaresoft nothing to lend what is already their most popular character in their best selling series for free. Anyone notice how Square didn't led any of their popular characters to Nintendo for the upcoming Mario basketball game? No, instead they threw in character types, because they aren't very popular, and thus Square can BENEFIT from them being tossed back in the limelight, unlike Cloud, Squall and every other NAMED Final fantasy character, who they can toss in any of their own games and charge you for.
So, the answer is simply no.
Andy