World of Warcraft has increasingly incorporated the sort of strict geographic progression you cite in Lord of the Rings Online and Everquest II. While quests in the "old world" often have you trekking out to the far corners of Azeroth, content in the Burning Crusade and Wrath of the Lich King expansions guides the player along a breadcrumb trail tying towns and regions together.

I have unfortunately, like most, neglected these seldom traveled places in World of Warcraft. While I do have some motivation to explore, the effort involved in traveling to an area in an attempt to find some previously unexplored relic or cave is enough of a barrier to discourage me from starting. If I spend twenty or thirty minutes running accross the world only to find an unexciting geometry, albeit a new landscape, then I feel like I wasted time that I could have spent towards activities that have more tangible rewards in the game.

What excited me about Star Wars Galaxies in the run up to its release was the prospect of being able to create your own content in these unexplored areas, to find that unexciting bit of Tatooine far from other civilization and start one of your own. I never got into SWG after release, and sadly that original vision did not last long, but I hope some day soon a developer realizes the marriage between a wide open world to explore and tools for players to shape and add to it.