The Nostalgia Critic's "Top 11 Cereal Mascots" episode is pretty good; it even includes an overview of all the different Cookie Crisp mascots, showing how a wizard evolved in a cops n' robbers team into a Tex Avery-style wolf.
I've always thought Sugar Bear was a little overrated. He thinks he's so cool, but unlike the Trix Rabbit or even Lucky, he doesn't seem to care much about his cereal. He may say he can't get enough of that Sugar Crisp, but he's so laid-back and blase about it, like he doesn't really care about the glorious prize. He's like a member of the Cereal Rat Pack.
I actually think Barney Rubble and Fred Flintstone deserve a place on the list. They may not qualify because they're known for other things besides cereal pushing, but by the time they did the commercials, they weren't doing a whole lot else. Unlike the Lucky Charms commercials, they actually make you root for the cereal thief -- but they can't make you root for early-'90s fake rap songs that contain the phrase "I'm here to say."