I think at this time my favorite map of a fictional world is the one depicted in the RPG Final Fantasy XII. It has a lot of detail. There are many other maps included within the game as well that show the detailed layout of specific areas.

As for cosmic maps, I have found that seeing the same constellations in the skies of almost all fictional worlds in video games that show the skies at night makes me wonder at the imagination of those that create the games. A very familiar constellation "Orion" shows up in multiple video games, and if you study the constellations that surround that one you will see that they too are familiar and in the same places relative to "Orion" as they are in the sky of Earth. Perhaps it is too much to create a world's own version of the night sky, although I have seen many games that did have their own skies.

As I have already indicated, the Final Fantasy video games seem to have some of the best maps; however, this is not by any means an exclusive. The maps included in "Oblivion" and the other games associated with that world are just as fantastic. I would also include the maps for many of the Legend of Zelda and the Metroid games. All of these maps have the detail that is needed to help you figure out where you are in the game, which to me is very important.

From time to time I hang different maps in a conspicuous place that can be readily accessed for reference while playing a video game related to that map. Sometimes I hang multiple maps of the same video game world to see and compare the differences and changes that have been made to that world across the series of games that have that world in them.