I heard Jungleland on the way in to work and would agree that it is the Springsteen song which I would most describe as Epic. There are other songs which are longer or more intense but the storytelling which changes the nature of Jungleland. Clarence's solo and following conclusion to the story are what drive it over to the top.
A possible other candidate is the 77 version of Backstreets from the Boston Music Hall stand:
Pivoting to non-Springsteen, I would throw "The Storm" by Big Country into the mix. If a song gets you to picture yourself standing on a wind and rain swept mountain top in Scotland, it is well on its way to Epic status.