1. Hershey's - Sure there are other chocolates, and better chocolates, but the Hershey bar is the quintessential chocolate bar. This is due to its ubiquitous nature.
2. Snicker's. Not my favorite, but a solid candy bar by any measure. Its popularity over the last several decades cannot be ignored.
3. Baby Ruth. A solid contender which benefits from its appearance in Caddy Shack.
4. Butterfingers. Tastes great fresh or stale, and really makes a solid showing in D.Q. Blizzards and pies.
5. Heath Bar. Toffee is old school, so it is often overlooked, but old school has its place. Also solid in Blizzards.
Milky Ways and Three Musketeers are never a true disappointment when freely available, like in the kids Halloween bag. They just don't make the top five.
Reese's are probably no more candy bars than are Nut Rolls, Hershey's Kisses, or M & M's. Good to great treats all, but not candy bars.
I don't know what to do with the Toblerone. Always enjoyable, but occupying a weird marketing position.
Mounds and Almond joys are more of a change of pace candy bar.
Chocolate covered cookies are not candy bars simply by inclusion in the candy section of the store.