Deadpool is the single most overrated comic book character in history. Batman at least has reasons people love him so much, but Deadpool has shitty meme-tier humor and isn't even that cool of a character.
And yes Aquaman is objectively cooler because if you read literally anything about Aquaman beyond "LOL HE TALKS TO FISH WHAT A NERD XD" you'd realize he's really badass.
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Deadpool is a statement on the anti-hero trope. He's a walking commentary on overused tropes in comic books. If you were smarter you would have understood that.