3. Star Wars
When George Lucas created Star Wars and set it in a distant galaxy, he created a vast playground for authors to use to this day. Unfortunately, like many other EUs, things got worse as time went on. At the beginning, it was just some comics and novels set before and during the original trilogy. Once Return of the Jedi was released, the Star Wars EU shifted focus and began exploring something the movies ignored if the Galactic Empire truly spanned the galaxy, wouldn't the war keep going? The response to this question was "Yes" and spawned some of the best and most beloved Star Wars EU material. Rogue and Wraith Squadrons, the Thrawn Trilogy, and countless other novels, comics, and games covered the Rebellion's long struggle to defeat the remnants of the Empire while transforming into the New Republic. But then came Dark Empire, and with it, a shift towards absurdity. It must be said that before Dark Empire, there was plenty of bad, mediocre, and/or ridiculous material. Even the Thrawn novels were marred by the notion that Thrawn could look at pieces of art from a certain culture and come up with strategic and tactical insights. But people were willing to gloss over things like that because the plots and characters were compelling and the stakes were reasonable. What Dark Empire did was introduce the notion of ultra-high stakes and the proliferation of super weapons. Dark Empire revolved around the return of Palpatine as a Force ghost who possessed clones of himself and built up a huge Imperial faction near the galaxy's core. In order to beat the New Republic, he created giant ships called World Devastators that ripped apart a planet's surface and used the materials to build more Devastators and other weapons. After Luke and Leia beat Palpatine and cause him to blow up a huge chunk of his fleet with what essentially amounted to a Force tornado, Palpatine came back and used the Galaxy Gun, which fired hyperspace capable missiles that could destroy planets. With the new standard set, more super weapons that rivaled the Death Star came out of the woodworks. The most infamous is probably the Sun Crusher, an almost invincible fighter sized ship that fired torpedoes that made suns go supernova. New galaxy spanning threats like the Yuuzhan Vong and the fact that there had never really been a stable peace in the post-ROTJ time frame meant that the entire Star Wars setting transformed into a horribly bleak setting on the verge of falling apart. What could make things worse? Force users popping up everywhere and almost every background character getting fleshed out for no reason. While people may argue the merits of Karen Traviss' take on the Mandalorians, its popularity is sign that people just can't stand getting force fed Force sensitive characters all the time, especially when authors turn them into walking no limits fallacies. Now that Disney is making a new Star Wars trilogy, a lot of the EU is probably going to be invalidated, but if we're lucky, we'll always have Mofference.