There's an interesting article that was published on the wonderful gaming industry news site, Next Generation
that asks the question, "Whatever happened to the videogame mascot?" Using Sega's mascot, Sonic the Hedgehog, as an example, Eric-Jon Rössel Waugh points to the rise and fall of the blue speed demon thanks to corporate mishandling and making games, "just for the sake of there being more Sonic games in the world."
It's an interesting article, and one that I'm sure will get gamers who grew up with mascots to get a little teary-eyed. But hey, at least we have Mario, right?"CULTURE: Mascots and Messages" (Next-Gen)EDIT
: Fixed broken link to Next-Gen article.