It's safe to say Iron Man is the most iconic character in the Marvel Cinematic Universe. When the 2008 movie used Robert Downey Jr. to bring Tony Stark to life, few fans could have predicted what Marvel Studios would create thereafter with the Avengers. All the same, Tony started it all, becoming the anchor for Nick Fury to start the Earth's Mightiest Heroes initiative early on.
Source:https://www.cbr.com/what-if-iron-man-crashed-into-grandmaster-ending-explained/