I've long been a fan of the D&D campaign based around exploration, both on a micro (dungeon) and macro (wilderness) level. No publisher highlighted this aspect of D&D better than Judges Guild, whose Wilderlands of High Fantasy setting was built around the idea that there was a lot of unexplored stuff out there. Sure, there were cities -- big ones, too -- but there was space. Bob Bledsaw's crowning achievement (other than the City State of the Invincible Overlord) was the Campaign Hexagon System and its specific implementation in the Wilderlands.
Be assured that the system was more than mere wilderness maps on hex paper. The first benefit of the system was that it was scalar, taking the DM from large-scale campaign hex maps to individual hex maps of a particular campaign hex to two scales of square-grid map for city plans and small scale dungeon floorplans. Like a nested Russian doll, the map scales all fit within each other.
The second benefit of the system was that Judges Guild published maps and blank sheets (the Fantasy Cartographer's Guide is simply wonderful) for keying said maps in large, easy-to-use booklets, and provided numerous tables and charts to help DMs populate those maps with terrain, features, monsters, and treasures as needed.
Lastly, Bledsaw ensured that all JG "content" publications actually used the Campaign Hexagon system, and took it to the next level with the inclusion of TWO maps for every wilderness area -- a DM's map and a player's map that was blank, other than coastlines and known features. Talk about an incentive to explore -- there was a whole map to fill out! And after that, 15 more in the Wilderlands setting. For my money, the Wilderlands Setting was the ultimate sandbox for OSR-style gaming. JG products were at their strongest when providing game aids to enable this style of sandbox play.
I am a huge fan of Greyhawk, but the exploration element and sense of the unknown is largely missing (at least in the aboveground of the Eastern Flanaess). The Greyhawk setting (and Faerun too, for the most part) is one of nations; the Wilderlands is one of wilderness, and is therefore the first setting that comes to mind when the "points of light" concept is bandied about.
Sadly, exploration as a player and character motivator seemingly became phased out as the game transformed into one of character customization and battlemat-driven tactical combat. I honestly can't remember the last time someone actually mapped in a 3.x game. I wonder if a raised-on-4th-edition player would even understand the point of mapping.