With so many existing superhero universes, it makes sense that some heroes are similar to others. Some of them have the same set of powers while others have been through similar experiences or would get along as friends thanks to their characterizations.
Both Arrowverse and Marvel have a lot of superheroes whose adventures the fans can watch/read. Some of them are more popular, others less, but regardless of how loved they are, Arrowverse heroes certainly have their Marvel counterparts.
Green Arrow And Hawkeye
This connection is obvious - both Green Arrow and Hawkeye are excellent archers and fighters who have no special powers. They're even more similar in the comics where Oliver Queen is more cheerful and not as grim as in the Arrowverse.
They also put a lot of emphasis on protecting their friends and even though other superheroes sometimes underestimate them, they can stand their ground and come out victorious in multiple fights.
Atom And Ant-Man
Ray Palmer doesn't need ants to transport around since his suit can fly. He also built it himself, unlike Scott Lang who got the suit from the original Ant-Man, Hank Pym.
They do have similar powers, though - shrinking down and growing big again. They also keep their strength even when they're small. Ray and Scott have a sense of humor and would probably enjoy hanging out together.
Flash And Quicksilver
Even though they have different backgrounds, they turned out to be similar in many ways. And it's not just their powers - even though both Barry Allen and Pietro Maximoff belong among the fastest men alive.
They also have a sense of humor and have experienced tragedy that made them value the people around them even more. Barry and Pietro are one of the younger superheroes which also influences the way they view the world around them.
Superman And Captain America
Unlike Captain America in the MCU, Superman hasn't had that much space in the Arrowverse. That should change with his and Lois Lane's upcoming TV show. Nevertheless, the similarities between them are obvious enough. Both are kind-hearted, honorable, and place a lot of emphasis on truth, justice, and the American way.
As a result, they became the symbols of America. Some fans might find them annoying thanks to their straight-cut personalities, but both Superman and Captain America mean well and want to help people.
Black Canary And Black Widow
The similarities in their superhero names aren't the only thing bounding Natasha Romanoff and Dinah Drake together. They had been through a lot, had less than ideal life, but still made the best of the circumstances they were in.
Natasha shares a similarity with another Black Canary, Laurel Lance - they were both willing to sacrifice their lives to make the world a better place.
Hawkman And Falcon
Aside from the obvious bird connection, Hawkman and Falcon have a lot in common.
Hawkman is an old soul, he's been around for centuries, but he continues to fight the good fight. Falcon is much younger, but he has just as strong a moral sense of what's right and wrong. Both of them also work best in a team - Hawkman alongside Hawkgirl, and Falcon with his good friend, Captain America, or with Bucky Barnes.
John Constantine And Doctor Strange
This connection seems obvious - both characters are wizards in a world full of superheroes who often aren't that excited about magic (such as Batman or Iron Man). They have a burden on their shoulders since they're mostly the only ones who can stop magical threats.
Their characters are similar as well - John Constantine and Stephen Strange are intelligent and snarky individuals with a biting sense of humor who don't always get along well with other people and struggle to build friendships sometimes.
Supergirl And Captain Marvel
Even though their approach to life is different - Supergirl is more optimistic, possibly thanks to her younger age, neither superhero lets others mess with her.
They have extraordinary powers in a world full of non-powered heroes which can make it difficult for others to connect with them. As a result of their powers, they have a lot of responsibility which can put a toll on them.
Sara Lance And Black Widow
Just like Black Canary, Sara Lance is also similar to Black Widow - possibly even more. Neither of them has any powers yet they end up becoming a part of a large team of mostly powered heroes.
They excel at hand-to-hand combat and have a dark past they continue to struggle with. As a result, they only open up to the people who are closest to them.
Caitlin Snow And Jean Grey
Finally, there's a similarity between Caitlin Snow and Jean Grey. Since Caitlin has to balance two personalities in her head, she would understand what Jean was going through in her 'Dark Phoenix' phase.
Neither of them has had that much luck in relationships, death often stepped in and made their lives miserable. What's more, both Caitlin and Jean are a part of a team and their team is also their family. As such, they have very little connection to the outside world.