Who would you replace with whom to make the story work with little to no changes? Why? For example:
Captain America replaced by Superman
Both are inspirational leaders with a straight-edge moral compass.
Iron Man replaced by Green Lantern
Both are characters with a comedic streak, heart of gold, and maverick, revel attitude.
Thor replaced by Wonder Woman
Both are warriors from a mythical culture, and both have a fish out of water story.
Hulk replaced by Cyborg
Both are intelligent heroes who feel cursed by their powers at first, but they then embrace them in a time of need.
Black Widow replaced by Batman
Both are stealthy, cunning, resourceful heroes without powers, who use gadgets. They both have a dark past. And they are both badass.
Nick Fury replaced by Amanda Waller
Both are the secret leader of some special military team.
Maria Hill replaced by Rick Flag
Both are the tough second-in-command of some special military team.
Phil Coulson replaced by Snapper Carr
Both are superhero fans who can come through when the chips are down.
Hawkeye replaced by Steve Trevor
They are both love interests with a connection to the female. Both have military connections. The female owes him something for a previous save.
Loki replaced by Fury
The villain with a connection to the fish out of water.
They look similar and serve their respective baddies
Thanos replaced by Darkseid
Both are conquering aliens who act as benefactors for the villain