The Path to Gaming Enlightenment

Emphasis on Setting not System
What makes for a fun, immersive gaming experience? A referee who has charisma and can come up with a good story on-the-fly, one who makes good decisions, is fair and cares about the players having fun certainly goes a long way. System does matter and the referee should choose a system he/she is familiar with and one that lends itself to telling the kind of stories the group wishes to explore. Speaking generally, I would say the rules are just the beginning, however. A great campaign rests on its milieu.
The authors of White Box seemed to know this intuitively (or through experience) and expect referees to put a lot of work into designing their own personal milieu. White Box implies certain aspects of setting, if one uses all the tools in the Box. A referee designing a campaign is free to pick and choose among the "guidelines" found in the LBBs and to invent new material to supplement or replace aspects of the game as written. I believe this was expected. It is certainly what many gamers turned authors did with the new hobby as evidenced by some of their published work. Arduin, Warlock, and Chivalry & Sorcery are three obvious examples of early players taking the ideas presented in the Three Little Brown Books and inventing their own milieu for play complete with rule changes and additions. While adapting rules to support the game they wanted to run at their table, they altered the original in such ways that they created at minimum a major variation and in the claim of some, a completely new game.
The Original Game in all its various editions, has inspired referees the world over to create countless settings for their personal use. Some borrowed heavily from other sources, effectively running their own version of Middle Earth or The Young Kingdoms. Others, like myself, took a little here and a little there from many sources of inspiration and blended it all together. Some settings received lavish publications and are so well known that mention by name - Dragonlance, Ravenloft, or Dark Sun - brings to mind a host of mental images. These three official settings, all published by TSR during its 2nd Edition era, illustrate how the game can be radically different depending on the setting. In many respects, the setting becomes more important than the game system. A great setting has character and personality of its own. A great setting helps the referee know how to handle unforeseen situations that arise at the table because of that very quality. The referee basically role-plays the setting.