Sonic imo, if I were to tier community reactions, he'd have his own tier at the top. Many of the people who were part of Brawl speculation grew up during that SNES vs Sega Genesis era, so other than the fact that Sonic is a titan of a video game character to begin with, the whole concept of being able to have Mario fight Sonic was a childhood dream come true for so many. His announcement even reached mainstream news sites, which for just a single addition to a video game was unheard of at the time. The circumstances were a bit different back then, Smash speculation wasn't as widespread as it was mostly restricted to dedicated forums, and characters were just dropped on the website at random rather than being at events where millions watch simultaneously, yet he still got such a strong reaction, in terms of pure excitement I don't think there's any comparison.
And that's coming from someone who at the time didn't even want Sonic in the game, I was too young to really appreciate the significance of his inclusion, but there's just no denying the impact it had. I'd say Sonic > Cloud > Banjo, although I think Mega Man is pretty underrated on the poll so far, the difference between Banjo and him wasn't that big.