Number 10: Captain America: The First Avenger
Taking the riskier approach of making Captain America’s MCU debut a period piece set in World War II could have backfired. But the classic storytelling made sense and helped firmly establish Captain America’s place as a man outside of time in the modern MCU.
Chris Evans was a great Human Torch in the Fantastic Four movies, but proved an even better Captain America. Unlike a lot of the other MCU films, Captain America actually had a respectable villain in The Red Skull.
Just as importantly, key elements of Captain America would become significant building blocks of the MCU. From the first Infinity Stone, introduction of Hydra and Agent Carter and the death of Bucky, core foundations of Marvel movies today were first touched on here.