Skittles would be way higher on this list if we could forget that time we put a whole bag in our mouth and cut the sh*t out of our cheeks due to all the sugar shrapnel that exploded everywhere. On the other hand, getting Skittles directly into your bloodstream is kind of amazing.
Nerds are basically little sugar boogers with a slight hint of fruit flavor, but they sadly don't come in flavor combo packs at Halloween. Dump random flavors in your mouth and hope for the best.
If they were embedded in a cookie or something, they might be #1, but on their own, M&Ms are still pretty great. Especially if they're the peanut kind. Or the peanut butter kind. Or the pretzel kind... actually, why don't they make a little bag with all the different flavors inside? That would put it in contention for the top five. Take heed, Mars.