Reddit user Cheesenaut for creating a rather simple to use guide on how the main characters of the MCU fit into the overall picture. Starting with Iron Man and feeding into Iron Man 2, you can see the other cornerstones of the MCU take their spots, with Thor, The Incredible Hulk, and Captain America: The First Avenger rounding out the group.
That, of course, led to the landmark Avengers film, which brought superheroes together like no other had before. The lines coming from each movie represent the main characters of that franchise, so in regard to Captain America: The First Avenger that would be Cap and Bucky, who shows up next in Captain America: The Winter Soldier. For Iron Man 2 it meant War Machine and Black Widow in addition to Iron Man himself, and for Thor it meant Thor, Loki, and Hawkeye.
ifesbob 