I was looking through the DC Comics wiki when I came across the entry for the Superman storyline "Fall of Metropolis". I read through the summary and, while I remember it when it came out, I never read story myself. Anyway, I was curious enough about it to see if I could get a trade for that storyline. Surprisingly, I couldn't find one, indicating that it was never "traded up."
This came as a surprise considering all the stuff that goes down in it, including the complete fall of Lex.
This got me thinking. What other storylines out there that have proven to be popular or important to the character that have never been collected together and you wish to see?