Help me, Comics Nerds!

[captain_slinky]

There was a semi-recent Superman story (happened before the New DCU 52 Zoo Crew Review) where Superman was shown why, for the good of Reality, he and the other super-heroes had to die or go away or stop being super heroes. Their existence and their continually saving the Earth was forcing a balance of entropy (or something) to continually throw worse and worse catastrophes at them. It lead to the extinction of the human race and all life on Earth, and I *think* it ended up with Jimmy Olson and Lois Lane being the last humans, and they die one by one, alone. It was super-depressing and powerful and I'd REALLY like to know which issue it was!

Help? Anyone??