PCs or World

What's at the Center of the Campaign?
Fantasy role-playing campaigns can be built a number of different ways to suit the individual tastes of the players. Much like the literature from which White Box and the hobby in general draws for inspiration, it is (almost) always a combination of (player) characters and world interacting. The cast of characters must have a stage or world on which to act out their story. Sometimes the story takes place over several generations and involves characters that come and go. The only constant in such a tale is the world or setting.
Narnia, C.S. Lewis' brilliant fantasy world is the setting for a number of fantastic tales. Other inspirational works which feature the world setting at center stage include George R.R. Martin's Game of Thrones tales and J.R.R. Tolkien's Middle Earth. All feature a changing cast of characters who shape the world, but the story seems centered on the world itself. The fantasy role-playing campaign can readily tell this kind of narrative with a cast of PCs, some who come and go, while the world lives on, changing and evolving in response to both the PCs and NPCs actions.
The Conan tales of R.E. Howard, Michael Moorcock's Elric and Fritz Leiber's Swords stories involving the daring escapades of Fafhrd and the Gray Mouser are set in very interesting make-believe lands, but are really the personal narratives of the central character(s). The fantastic world provides a backdrop to the lives and adventures of the principle actors. A role-playing campaign can certainly take a similar approach and facilitate the story of PCs as they go from one adventure to the next. Continuity in such a campaign rests on the survival of the central cast, obviously. Old School games such as White Box frequently have high PC mortality rates, especially for low-level PCs and therefore may require some rule adjustments in order for the campaign to be centered on the activities of a single set of characters.
White Box and other systems in which PC life can be cheap (especially at lower levels) and players may expect to go through a number of characters during the campaign lend themselves more to the "world as central feature" narrative. White Box is cleverly designed so that as the PC progresses up the level ladder, the players have more options for keeping them alive. Higher hit points and the availability of resurrection supports PC survival and the resulting story shifting center toward the exploits of the high level PC. Thus White Box is both Narnia and Conan.
The actual game setting can be as detailed as the referee wants to make it. Some campaigns run for years as nothing more than a common cast of characters that are linked by playing in several stand-alone adventures which taken together form an episodic campaign. Other campaigns involve worlds borrowed from published works, either fiction or game materials. The game worlds I generally enjoy most, however are the personal creations of gaming buddies, some of which are the result of years (or decades) of play.
Campaigns, even the episodic type, tend to develop a certain character of their own. Whether dark and dangerous, light and humorous, heroic, gonzo or gothic in nature, each campaign will develop along distinct lines and the players will associate it with certain key events, places and maybe characters. Each campaign tells it's own story through play, sometimes with the aid of heavy scripting from the referee, but I tend to favor letting the story happen as a result of the players interacting with the world through the PCs. As a referee I greatly enjoy being surprised by PC response to my world where a number of opportunities are always available and things are constantly changing, with or without PC intervention.