In the decade since the release of Iron Man, the MCU has turned into a universe-sprawling, massive franchise that everyone in Hollywood wants to emulate.
Iron Man, at the time of its release a decade ago, centered on a character that was in no way familiar to those in the mainstream.
Iron Man was released on May 2, 2008, and thus, the MCU was born.
Without Iron Man succeeding in such a way, the MCU as we know it may not exist.