What makes fantasy and fiction great? Not just the story and the main characters, but the attention to details and the fleshing out of an imaginary but almost completely real world.
By creating history, backgrounds and minor characters seem just as important as the main ones, authors, screenwriters and video game designers manage to capture our imaginations, and maps, made by the creators or by fans, are just as important to getting the full experience.
The Realm of Middle Earth (Lord of the Rings)
Westeros & Essos (A Song of Ice and Fire)
The Star Wars Galaxy
Hogwarts (Harry Potter)
Star Trek Universe
Planet of Azeroth (Warcraft Universe)
The Island (Lost)
Continent of Tamriel (Elder Scrolls Games)
Planet of Arrakis (Dune)
The Continent (The Witcher)
Springfield (The Simpsons)
You can find more maps like these on this fantastic blog.
My favorite fictional world is the one of A Song of Ice and Fire, so this post about maps of places on Westeros and Essos is my obvious recommendation.