"There is always a bit of truth. In Legends." ~ Ahsoka Tano
Expanded Universe (EU) also known as Legends is the vast Universe of books, comics, novels, games and everything else related to Star Wars universe prior to Disney buying the rights to the franchise.
Over the span of ~ 40 years EU gave birth to numerous stories, characters, ships, Force abilities, species, planets and moments that topped anything seen in the movies and even going so far to make George Lucas surprised and proud. Some of the EU parts were "canonized" to some extent and form. Like the Ones, Darth Bane, Admrial Thrawn, Han and Leia son (Though Ben is really lame when compared to Jacen)...
Over the awesome parts of EU like Darth Revan, Skywalker family, Mara Jade, Solo family, Darth Plagueis, Abeloth, Dark Empire, Clone Wars, New Republic, Old Republic, X-Wings, Legacy series, Starkiller, Infinities, many Siths and Jedis and a lot more, what would you like to see in the future Disney projects (Comics, Movies, TV..) ?? If they chose to do it?