SOLO
-Spider-Man No More! (ASM#50): A one-shot when Peter decides not to be SM anymore, but finally went back. It inspired SM2 and ASM2 movies, very important
-The Night Gwen Stacy Died (ASM#121-122): The arc when dies the first love of Peter at the hands of Green Goblin, essencial
-The First Clone Saga (ASM#141-151): Made in 70s, the Jackal appears for first time and makes clones of Gwen Stacey and Peter himself. It inspired the very-long-and-boring 90s Clone Saga and it's way better than that
-Maximum Carnage (numbers here): The origin of Carnage and the first Spidey-Venom alliance to stop him, totally recommendable
-The Clone Saga (6-issue miniseries): Made in 2009 as a retold of the whole 90s Clone Saga with a different ending (Ben Reilly didn't die and the Peter & Mary Jane baby was safe) that could explain MC2's alternate universe where exists May "Mayday" Parker aka Spider-Girl
-Back in Black (ASM#539-543): Post-Civil War consequence, after hurting Uncle May and leaving her close to death, Peter stop containing him and goes for revenge against the ones who did this to her aunt, so he put once again his black costume (former Symbiote look) in a personal vendetta. Very awesome read
-New Ways to Die (ASM#568-573): One of the few stories I like from Spidey after "One More Day" and "Brand New Day", also the reborn of Eddie Brock as the Anti-Venom, one of the few arcs I like from Slott
CROSSOVERS
-Secret Wars (12-issue miniseries): Spidey was part of the heroes team reunited by an entity against another team of villains. Here he got the black suit for first time, which was eventually the symbiote that is Venom
-Civil War (CW#1-7 & ASM#532-538): Spiderman allied to Ironman and the Register Act, and he revealed his identity as Peter Parker, but soon he found that he choosed the wrong side. Details in his ASM series

SOLO
-A Death in the Family (Batman#426-429): Basically the death of 2nd Robin (Jason Todd) at the hands of the Joker, brutal
-Knightfall (numbers here): When Bane first appeared and broke Batman's spine. Base for Nolan's DKR and the Batman version of The Death of Superman
-The Killing Joke (graphic novel): The Joker origin are shown, and also he left Barbara Gordon/Batgirl crippled and tried to make Jim Gordon insane
-Arkham Asylum (graphic novel): Batman goes for the Joker to Arkham facing the danger of all his villains caged there, and also shown the origin of the asylum. Drawn by the guy who make Sandman covers (very surrealist drawings) and base for Batman: Arkham Asylum game (and all Batman: Arkham series)
-Hush (Batman #608-619): A complex web Batman has to unveil that involves almost all his most known enemies, all orchestred by a new villain called just as Hush
-Under the Red Hood (Batman#635-641, 645-650, Annual#25): A new incarnation of Red Hood (previously was the Joker before his transformation) that resulted to be a revived Jason Todd
-Battle for the Cowl (3-issue miniseries): After the death of Batman, started the search of his sucessor, being Nightwing, Robin V (Damian Wayne), Robin III/Red Robin (Tim Drake)... and even Two-Faces and Red Hood who wanted to take the mantle
-The Return of Bruce Wayne (6-issue miniseries): The Darkseid's Omega Ray didn't kill Batman, just sent him back in time, so he has to be Batman again crossing different times like Prehistory, Wild West and Noir time
CROSSOVERS
-Identity Crisis (12-issue miniseries): A big conspiration behind the death of Elongatyed Man's wife that involved a lot of superheroes, Batman included. Consequences will be the prior events that leaded to Infinite Crisis
-Infinite Crisis (7-issue miniseries + Secret Origins): Here Batman has a major role as part of the superhero against Alexander Luthor from Earth-3 and Superboy Prime. Also, because of the altered reality by Superboy Prime, Jason Todd is revived and eventually will convert into the new Red Hood
-Final Crisis (7-issue miniseries): Also an important part in this crossover, but in the end was dead by Darkseid... but not really as it's seen in The Return of Bruce Wayne