Alan Moore's MiracleMan, (GOAT) The Killing Joke, Dark Knight Returns, Kingdom Come, Death of Superman, Knightfall, ICON: A Hero's Welcome (RIP Dwayne McDuffie), No Man's Land, Batman RIP, World War Hulk, The Death of Clark Kent, Star Wars - Legacy
Spidey Clone Saga, Age of Apoc (original), Onslaught, Civil War, Annihilation, Superboy Prime story arc, Burning Martian..several Daredevil arcs, can't recall the names..
"The Bar With No Name" issues from Captain America. The Scourge came through and REALLY knocked down the buildings...or at least shot them bitches down.
The "Mutant Massacre", "X-tinction Agenda", "The Shadow King" (right before the X teams merged into the Blue and Gold teams).
infinity Gauntlet, the storyline where the the grey & green Hulks and Banner all merge into one being, Civil War.
Yeah this shit is taking forever, but I'm very entertained by it. It feels like I'll never catch up to the present though lmao. So many different series going on.
So are we naming runs or crossovers or landmark stories...?
whatever...
Annihilation (the best crossover I have ever read)
Sinestro Corps War (the best Geoff Johns X-over Ive ever read)
Hush (yeah its overrated and Loeb kinda sucks but it has spot on characterization/great dialogue, art is beautiful and got me interested in Batman...like a good summer blockbuster movie)
Batman: Year One (IMO best Batman story ever)
Legion of 3 Worlds (second best Johns x-over ever)
DC One Million (slept on Morrison event)
Civil War (the most important x-over since COIE. Changed the entire Marvel U for a good while).
I got the whole AoA saga as a torrent. It's easy to find if you just google specific issues. Usually they end with .cbr or .rar if it's a group of issues.