Mascots and Messages
Next Generation has an insightful, detailed look at Sonic's life as Sega mascot, as well as theorizing a little about what makes a mascot powerful and relevant, or dated and out-of-touch.
When Sonic started off, he was one of the most well-conceived mascots probably in the history of mascotdom. Sega's console was faster than the competition's, so Sonic was super fast. Sega was the scrappy underdog, effortlessly showing up the "big guys", so Sonic was full of attitude. Sega's logo was blue, so Sonic was blue. The Genesis was targeted toward kids who were growing out of the NES, so Sonic was a sleek teenager (compared to the fuddy uncle Nintendo had going, who by comparison seemed to represent the "past generation").