@Green_vs_Red:
And yet Mr Game and Watch was in melee and brawl despite being older than god and less relevant than Jim Carrey's movie career. Also I don't see how the reception of the last GS game should affect the possible addition of a GS character particularly from the GBA games, I know that mentality didn't stop them from adding Ness in the first Smash Bros. game (despite the Earthbound's horrible NA sales) and most certainly not Megaman whose last game wasn't exactly beloved by fans either.
Not even close to being the same thing.
The Game and Watch was pretty much one of the first great successful entries by Nintendo in the video game business. If it hadn't been for that success Nintendo would not be where it is right now. So regardless of Game and Watches not being common at present, the inclusion of Mr. Game and Watch still acknowledges the legacy of Nintendo.
Golden Sun did no such thing. It was just another franchise that came out. And sure, people loved it and Camelot did a fantastic job with it. But the time when it was truly relevant was the GBA era, especially since the last iteration on DS was meant to continue it and it failed miserably to make a splash.
Don't get me wrong, I like Golden Sun and believe it's an astounding series, but it has no more merit of being in Smash than Sin & Punishment.
Add to that the fact that Sakurai is struggling with the roster size and it's very unlikely that a Golden Sun character will earn a spot against currently more relevant characters, like say those from Xenoblade.
edit: Oh yea, as for Ness, we're talking about the Mother series being a successful franchise in Japan at the time, and Mega Man was included due to being easily the most wanted for Brawl along with Sonic, not to mention an extremely iconic video game character who helped sell as many NES systems as most Nintendo games.