10. It Requires An Awful Lot Of Background KnowledgeMarvel released five films before The Avengers, introducing characters and plot devices, laying the groundwork which would culminate in this astonishing movie. This was a good thing to do, as it meant most people already had a rudimentary understanding of the concept of the shared universe and the characters that exist within it, as well as theoretically meaning that most of the plot devices had already been introduced. However, not everyone is as engrossed in the MCU as us comic book fans average viewers would have been lost by many parts of the film. The first Thor film introduced the primary villain, and without seeing Captain America: The First Avenger you would have been completely lost as to what the tesseract is, why it is on earth and how it ended up in the hands of SHIELD. Iron Man 2 was pretty much a piece of required viewing as it introduced SHIELD, Black Widow and Nick Fury to the Marvel Cinematic Universe, as well as making Phil Coulson one of Marvel's most popular characters. Without seeing these films The Avengers makes very little sense, so it is hardly the most accesible of films for mainstream audiences.