I don't know the statistics,but it seems likely to me that Captain America's origin story has been told and retold more times than any other hero from mighty Marvel. The first time I came across the original Joe Simon and Jack Kirby version of the epic origin was in the pages of Jules Feiffer's The Great Comic Book Heroes. The splash page for "Case No. 1 - Meet Captain America" above started it all as we see a young and willing Steve Rogers become the physically and mentally improved Captain America thanks to the serum developed by Doctor Reinstein.
Cap immediately begins to battle the villains of the day and also takes on a young partner named Bucky.
During the Silver Age revival of Captain America in Tales of Suspense #63 we get the origin retold. This 1965 version is pretty much the same as the Golden Age 1941 original but rendered in Kirby's more potent Silver Age style. Inked by Frank Giacoia these are muscular pencils which tell the story of the Super Soldier serum with power.
This version does get a bit more battlefield action with Cap and Bucky and it also marks the beginning of re-tellings of other Golden Age Cap stories.
And not that much later in Captain America #109 Stan and Jack tell the story again, this time with a full-fledged comic to tell the story. Longtime Cap artist Syd Shores is inking the Kirby pencils on this 1968 effort and and it's a tour de force artistically. The story of the origin itself introduces a completely new element into the process, the Vita-Rays which acted in concert with the vaunted Super-Soldier Serum to make Cap the man he became.
Cap's origin story is a vital one and it's important in comics to recognize that new readers come along all the time and taking proper care of those readers is crucible in making a character durable through the years.