Superman’s always fighting for truth, justice and the American way but that doesn’t leave him much room for dramatic depth. Batman on the other hand is a morally complex character who walks the grey area of right and wrong. Behind all the wealth and bat-gadgets he’s also a troubled guy who has experienced painful loss and traumatic events more times than most humans should. This makes him more interesting.
He’s a man who has to constantly risk his life against city level threats knowing that one straight slip and he’d be dead. That’s the mark of a true hero and that’s what makes Batman so compelling. He’s a flawed character that has to work extremely hard at what he does because the alternative is just too terrible.
When it comes to 1v1 battles, Batman is easily superior to Superman. The Man of Steel has super senses, super speed and super everything else but if he was to ever come up against Batman he’d be toast in about a second. Batman has a whole bunch of tricks up his sleeve and he’s always ready with a plan.
This is what separates him from other heroes like Superman. He’s a hero that doesn’t just take on demigods and planet busting aliens, he takes them on with his brains and his brawn. That’s why he’s the best superhero of all time.