From Diablo Wiki
There is no ranger class or monster in Diablo III, but the term is commonly used for archer type characters in many RPGs. The Demon Hunter class was original envisioned as a desert ranger, wearing garments of cloth, with flowing robes and a camouflaging cape.
During development the class was given a tweak away from the traditional RPG archetype, and modified into the goth, leather-wearing Demon Hunter. Compilations of early concept art make for an interesting visual comparison.
The design of the Archer / Demon Hunter was detailed in a series of slides during the Blizzcon 2010 Gameplay Panel.
Fan Class Ranger
Prior to the reveal of the Demon Hunter, fans spent much time theorizing what Diablo III's archer class would look and play like. See the Fan class Archer for a well thought out version of the class.