Unabashedly stealing @bigblock66’s format to create a list here.
Superman is my favorite character. Here’s an old post that explains the why and how.
If Superman didn’t exist my favorite DC character would be Wonder Woman. She’s one of the most powerful characters in the DC Universe, a demigod, yet one of the kindest, most compassionate as well. If Superman is the moral center of the DC Trinity, and Batman is its mind, then Wonder Woman is its heart. Admittedly, though she’s high on my list, I need to read more of her stories.
If Wonder Woman didn’t exist, my favorite character would be, no surprise here, Batman. I mean, he’s the face of DC, no doubt about it. A brilliant detective, a tactician that has a plan for almost everything, a billionaire with some of the most amazing tech aiding him in his crusade against crime, a regular man that pushed his body and mind to its absolute limits to make himself the best of the best. Just an all around cool character.
If Batman didn’t exist, my favorite DC character would be a Green Lantern, probably Hal Jordan or John Stewart. I like space sci fi, and Green Lantern stories provide that, but they also provide it mixed with some mystical elements (power rings, Guardians, etc). I like Hal’s swagger, and John’s no nonsense attitude.
If Green Lantern didn’t exist, my favorite DC character would be Cyborg. Admittedly, this is about the concept and power set. Being digitally connected to everything and having a built-in arsenal of weapons is pretty cool. I also like the ying and yang of his human side vs machine side.
If Cyborg didn’t exist, my favorite DC character would be Green Arrow. The CW show really elevated this character for me. Some of the best fight scenes on TV, coupled with quite a bit of heart. I like him in the comics too, with his quick wit and undying love for Black Canary. Their panels together are always fun.
If Green Arrow didn’t exist, my favorite DC character would be Harley Quinn. I’m a bit surprised I just wrote that. I’m usually into the more powerful characters, but lately I’ve been liking Harley more & more, especially the current version, as opposed to a pure villain. She’s one of few characters in DC that make me laugh, both on the page and on the screen. She’s got more layers than her fun, humorous attitude lets on. Also she’s a sneaky capable fighter that’s stood up to both villains and superheroes.
Then again… I’ve already mentioned “if Batman didn’t exist”, so at this point he’s off the board. Would Harley exist as the antihero we know today without Bats? I’m gonna give her some credit and say she would see the light on her own 
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