I think it'd have to be Pikachu is only for the 15 and under demographic. (Well and the parents that buy their kids this stuff.)
Actually something I hadn't thought about before. Not sure if that's a bigger knock against sonic, or just a compliment for Nintendo and their ability to seemingly create huge mascots anytime they want.
In another 10 years or so, i could argueably see Pikachu passing Mario.