One of the worst cereals I've tried was the Sour Patch one. It was only 99 cents and I was curious enough to give it a shot but it was terrible. Though I'd still prefer it over something with raisins.
My favorite cereal is the Honey Bunches of Oats with granola and almond, it's always filling and tastes great. Some other good ones are Cinnamon Toast Crunch (particularly the churros version) and Cookie Crisp. As a kid, my parents only really got me plain Corn Flakes and occasionally Cheerios or Kix which I'm sorta glad for now since those were the healthier options.