First of all, I completely disagree with the expected amount of "care" you're supposed to put into any fictional character regardless of exposure. A character can receive a following if he/she says one word. Hell, I'm sure there's plenty. I don't think they have to verify their existence becasue they were created for a purpose that normally doesn't lead to attachments. No, I am not particularly attached to any cereal mascots (outside Lucky, hope he kills those damn kids one day) but saying it's impossible and lowering your opinion of someone that does is just silly.
Second, Dante is definitely not comparable to a cereal mascot. Good or bad, a history has been established surrounding him and his family. He doesn't just advertise a product, he feels emotions. I don't want to argue the depth of his character becasue that's another discussion entirely but there's definitely more to him than "Follow your nose!"