I here ya. To me the story was simple and straight forward. Loki's embittered about not being king so he finds a world he believes he can rule over, Earth and he enlists an army to help him in his conquest, the price being Loki refreshing and handing over the Tasseract. Now of course, Earth isn't just going to sit there and be invaded, hence the Avengers group up and fight off the invasion. Simple and straightforward.