Marvel Comics has long had varying universes away from the standard Earth-616, with some fantastic stories in them. They really let the writers explore the characters, while letting them be creative with impunity.
So far, the MCU has avoided anything like this, sticking with them all in the same continuity. Spider-Verse attacked multiverses head on, but they’re the exception, not the rule.
The closest the other movies have to come to anything even resembling a multiverse are the X-Men and the MCU existing on a separate level to each other. Even then, with the recent acquisition of 20th Century Fox that’s no longer even the case.
The Stewart/McEllen (or McAvoy/Fassbender for the younger versions) version of the X-Men is set to be consigned to the history books, with new versions of the characters to be introduced to the MCU in due time.
Or rather, so it would seem.
The recent trailer for Spider-Man: Far From Home suggested that Mysterio might be from an alternate universe, opening the door to this becoming a staple of the MCU going forward.
Of course, with it being Mysterio he might just be lying, but that’s nowhere near as fun to think about. So, in honour of Far From Home's apparent multiverse-themed story, here are the best alternate reality comics Marvel have ever published.