As I wrote this list I realized that almost everything you like as a kid gets worse as you get older. Except maybe ice cream, pizza and chicken fingers. I think the following are still worth listing.
  1. Bubble gum flavored things
    Toothpaste especially
  2. Mini golf
    I remember really loving mini golf as a kid. Whenever someone suggests this as a grown up activity, I want to blow my brains out.
  3. Your parents' jokes
    Though at a certain age I think they get better again. One of the horrors of aging.
  4. Clowns
    Obvious but important
  5. Ketchup
    Not that it's bad, just not as good as when you were a kid.
  6. Popsicles
  7. Cotton candy