Dozens of individuals around the world claimed to have had heavenly visions, much like Joseph Smith. This episodes highlights eighteen of those individuals who gave their accounts before 1832 (with one in 1838 from a member of the Church). 
These individuals are as follows: 
Catharine Hummer in 1786, the Richards Brothers in 1794, David Brainerd in 1812, Benjamin Abbott in 1813, Lorenzo Dow in 1814, Rachel Baker in 1814, Norris Stearns in 1815, Elias Smith in 1816, *Charles G. Finney in 1821, Benjamin Putnam in 1821, Asa Wild in 1823, Alexander Campbell in 1824, Billy Hibbard in 1825, John S. Thompson in 1826, Solomon Chamberlin in 1829, Martin Harris in 1831, Harriet Tubman in 1832, and James G. Marsh in 1838 (just before Joseph Smith gave his most in-depth account that became the canonized version).
Why is Joseph Smith's first vision so foundational to the Church of Jesus Christ of Latter-day Saints when it wasn't written down until twelve years later, no one was told of the vision before joining the Church, Heavenly Father didn't become a character in the vision until eighteen years later, and dozens of individuals were also having visions of God and Jesus Christ?
How could Joseph Smith's first vision be "the greatest event in world history since [Jesus Christ]" if it seems by all accounts never to have happened?