Game Lore.....or the historical fiction world of a game provides the context for all characters. The most effective game lore's have connections to the real world, ancient history, mythology and other famous fictional lores.....such as Lord of the Rings by Tolkein.
Tolkein's lore is so effective because it actually is an "analog" of World War II. Tolkien was born before the Great War (World War I) and that generation had a firm belief in the "good of man." Many from that generation died in WWI and the thinking of the time was that "idealism" died in that war. This, in Tolkein's generation, was the main reason for World War II......they thought that evil (e.g., power hungry dictators, etc.) had become more powerful than normal man and "good." Tolkein saw WWII as a great battle against the spirit of evil....more than just a fight against Hitler, Mussolini and Stalin.
So fundamentally, all game Lore relates at some level to the struggle between good and evil. The more the Lore provides recognizable signposts to those playing of good and evil themes....the more that particular game lore will touch on something deep within each Gamer. As such, a well researched understanding of basic mythology, common cultural heritages and key theological themes will greatly enhance the "feel" of a gamer's world.
Good luck to all those creating their worlds!