Batman: The Dark Knight Returns, Concrete, Daredevil: Born Again, the launch of Marvel's New Universe line, The 'Nam, Superman: The Man of Steel, The Punisher mini-series, Booster Gold, Legends, Maus and.... ummm....
Think that's enough?
3. SECRET WARS AND CRISIS ON INFINITE EARTHS
Say what you will about them both (and you will,) these books were the perfect encapsulation of their respective universes.
In Secret Wars, you had the Marvel heroes doing what they do best: fight the villains, fight each others and then sort of team-up with everyone to fight the common threat and then sort start back from... uh... whence they came and put She-Hulk on someone's team and get new costumes and stuff.
With DC's Crisis, we got to see DC admit, for the first time, that they had have the deepest catalogue of characters in publishing and that their publishing history was really, really complicated.
But hell, we got some incredible art from the pairing of George Perez and Jerry Ordway and the deaths of the Golden Age Superman and Lois Lane, Barry Allen and Supergirl, moments that to this day still resonate with fans.