In the 1980's it was.
I haven't heard anything about it in a very long time. It certainly deserves to be one of the most famous.
In support of your point, it has been reprinted quite a few times:
• The Greatest Superman Stories Ever Told (DC, 1987 series, tpb) #1 (1987)
• The Greatest Superman Stories Ever Told (DC, 1987 series, hc) ([November] 1987)
• Across the Universe: The DC Universe Stories of Alan Moore (DC, 2003 series) ([June] 2003)
• DC Universe: The Stories of Alan Moore (DC, 2006 series) ([January] 2006)
• Superman: Whatever Happened to the Man of Tomorrow? The Deluxe Edition (DC, 2009 series, hardcover) ([July] 2009)
• Superman: A Celebration of 75 Years (DC, 2013 series) ([November] 2013)
• Superman vs. Mongul (DC, 2013 series) ([December] 2013)
Plus foreign language reprint editions.
