I suppose it’s debatable what falls under a blanket term like “Marvel Cosmic”. There are many series like Avengers that deal with some pretty cosmic events at times, but when I say it, I just mean the (mostly) strictly cosmic characters and events, most of which are from the same small handful of people and originate from the work of Jim Starlin (and usually involving Thanos somehow…).
Back in the olden days, before I was even alive, Jim Starlin started writing comics with Captain Marvel and Warlock and promptly made them more cosmic than ever before and introduced many classic characters like Thanos, Drax, Gamora, and everyone’s favorite troll, Pip. His Captain Marvel run is actually pretty rough and I don’t know how highly I’d recommend that one, but it’s nice to see the first appearance of Thanos and his often mentioned first attempt to destroy everything with the Cosmic Cube, and it’s very interesting to me to see the gradual improvement in Starlin’s writing and art through his first effort.
By the time he gets around to Warlock, his style has improved quite a bit and is much nearer to his level of quality in things like Dreadstar and Infinity Gauntlet and etc. It’s a little out there and is forced to wrap up all too quickly for it to quite reach the status of “cosmic epic”, but it’s definitely a worthwhile read and Infinity Gauntlet picks up pretty much right where Warlock left off.
Also worth mentioning at this point are the Silver Surfer and Quasar series’ of the 80s, that preceded Starlin’s big return with the Infinity so and sos. They are both pretty good for most of their runs until the awful mid-90s dark ages begins, which is right around the same time the whole cosmic side of Marvel at the time pretty much just collapses anyway.
The infamous Infinity Gauntlet event is still as good I remember it and packed full of massive cosmic chaos, with just about every major hero dying (for a few seconds) and every big cosmic entity coming out to play. Warlock got his own new spinoff book out of it, Warlock and the Infinity Watch, which again, ran on throughout the various Infinity affairs and up until the 90s came along and crushed it.
With the success of Infinity Gauntlet, Starlin went all out and dropped two more galaxy shattering Infinity events on the Marvel universe, Infinity War and Infinity Crusade.
Neither was quite as well received or as grand in scale, but they were both still really good cosmic tales in their own ways. I get the feeling Starlin was struggling a bit with Marvel wanting him to include more and more of their Earth-bound superheroes, yet also have less death and destruction involved. He did as he was asked, but makes it pretty clear that he viewed all these characters as nothing more than cannon fodder, while his favorites, Warlock and Thanos, did most of the real work. Oh wellllllll!
Once Infinity Crusade wrapped up, things quickly began going downhill for the cosmic book as those dreaded mid-90s arrived. There were a few decent stories left in the various cosmic books, but most of them suddenly found themselves saddled with godawful budget 90s artists like Tom Grindberg, and wouldn’t you know it, suddenly no one wanted to read any of these books anymore! (Yes. Note to self: don’t even try to read Silver Surfer past #100 or Quasar past #50. Big mistake.)
The cosmic side of Marvel pretty much just crawled into a dark corner and died quietly, not to be spoken of again for most of the next decade, except for a few rare last gasps like Starlin’s unfortunately failed attempts to revive them in Infinity Abyss and Marvel: The End…
…and Peter David’s criminally underrated Captain Marvel run. Other than that, it was pretty quiet out there in space until Annihilation came along, but that’s a tale for another time…