My best ever are still:
Corn Pops
Cinnamon Toast Crunch
Golden Grams
Frosted Flakes
Honey Nut Cheerios
Stuff that used to be good:
Trix, when it was still shaped like fruit.
Lucky Charms, same as Trix it was better when the marshmallows were shaped like charms.
Cookie Crisp, back when it didn't taste like poison.
Coco Pebbles, back when I was a kid and didn't mind chasing tiny food.
Fruit Loops, I don't know why.
Apple Jacks, same as Fruit Loops but worse.
Captain Crunch, now it just makes my mouth bleed.
I never liked cereal in milk so I always ate it dry, probably why I cannot stand more adult cereals. Spent about 10 years without eating any cereal but now I have kids so I get to show them the good stuff. I usually get to eat about one bowl of any given box but even my 5 year olds know not to touch my Corn Pops.