To get good insightful answers, how the question is framed matters. I missed an opportunity on Thursday
I listened intently to the National Geographic vinyl record of the Apollo 11 as a child in the late 1980s; space was a frontier humanity was going to colonize by 2020. I was memorized by the story of Apollo 11, only to later learn of Apollo 13; the "successful failure" as it has become known.
I've come to view Apollo 8 as the most important of the missions; the unknowns much greater than any other mission.
The Register, a British tech news site I greatly enjoy, provides great space exploration commentary, and their piece marking today's 50th anniversary of the Apollo 13 launch does not disappoint.