Okay, somebody deleted my addition
Stupid Wiki-nazis... Just because "LOL SONIC ISN'T ON THE LIST IT CAN'T BE REAL ZOMG IT'S JUST A BUNCHA 15 YEAR OLDS READING GOOGLE TRANSLATOR" doesn't mean it isn't fact. *******s.
ANYWAYS >.>
The letters Sakurai selected were ones he thought were good ideas, right? So if he selects a "good idea" more than once, that must mean he thinks it's a "really good idea?"
I think we can confirm, then, that King Dedede is in the game. If he actually read a letter, went "wow, that's cool," posted it, then found the same idea, went "wow, that's still cool," posted it, and kept going... he must really like that idea. I know you can easily debunk this theory by going "lol, we're not sakurai so we don't know," but just hang with it. I think it's worth something.
And for that, we could say that any idea he posted more than once must've been something he actually went "wow" and considered. It doesn't guarantee it, but geez... he put King Dedede in there, relatively, a LOT. And look at the four voted characters. Geno must've really intrigued him to appear that many times. Or Krystal. Or Ike. I think taking these numbers and looking at these "most popular characters" we can get a really good idea of what he's thinking for a roster.
Of course, there's still the NSider forums, which would screw it all up with all their suggestions being on the complete opposite end of the spectrum >.<