Okay, I want you to do me a favor.
Imagine the Riddler. One of Batman's most famous foes. Imagine him armed with a machine gun. Imagine him shooting sick people in a hospital.
Is it horrible? Sure. But does it have anything to do with what Riddler normally does? Is it completely out of character for him to do such a thing? And is it... kinda disappointing that a bad guy who does terrible things in extremely creative ways that only he does would do just... THAT?
Do you feel cheated since you were promised a Riddler story, and all you got was a standard story about a sicko who does something horrifying yet not that much in character? A character you love to hate?
There. Right there.
THAT is why the Joker sucks right now.
Ever since "The Killing Joke", writers have done all they can to keep the spirit of that Joker shown in a story that actually wasn't suppose to be canon(but it was popular, so there's that). Joker is Batman's arch enemy since he is the worst of the worst. So he has to do something inhumane to keep this status.
... Meaning two things.
First of all, the enemy relationship between the Clown Prince of Crime and the Dark Knight lacks creativity. Good hero-villain relationships has something extra, something that makes what they have unique. Like that Lex Luthor hates Superman for being better than him, so he tries to kill him so he can be the world's TRUE champion. Or how Spider-Man and Green Goblin's feud is a fight between geniuses and Peter is essentially part of Osborn's midlife crisis. Or Roy Harper and Cheshire share a daughter, making their relationship VERY complicated.
But the Joker and Batman? Batman hates Joker because he is an extremely disgusting human being. But that is a regular reason to hate him. Joker is obsessed with Batman, but WHY is he obsessed with him? Writers can't seem to agree on it. Their relationship lacks identity.
The SECOND problem with Joker being Batman's worst enemy is that... well, he is JUST that. His worst enemy. He is basically JUST the guy who pushes Batsy's buttons. Whenever something bad should happen to Batman, it was usually the Joker who had to do it since that was kind of a rule, EVEN if it was out of character. Like in "Death of The Family" event... more of THAT later.
Anyways, let us talk about the Joker's lack of personality. In the past, whatever Joker did something, it had a humorous element of a sort. Like he was pranking someone in an evil way. Like the time he poisoned every single fish in Gotham, NOT in order to kill people... but to make fishes look like him. Then, he argues that he should be paid since they looked like him. And he then tells a copyright clerk to fix it so he get paid for every fish that gets sold, something the poor clerk has no power over.
THAT is funny. In a twisted way. The Joker is a performer and a comedian. Whatever he does is ridicules, twisted, yet still has a touch of humor, a gag of some sort. Admit it, you thought it was a little funny when the Joker performed the pencil trick in "Dark Knight."
But since Joker has to outdo himself all the time by being the most horrible human being in the world, the writers sometimes forget to ad the small touch of humor.
Like in "Death of the Family", one of the more recent big Joker story-lines, where the Joker has cut off his face, wears it as a mask, and then tries to murder all of Batman's allies and friends since he thinks they hold him back.
... But how is it funny? Where is the punchline?
There IS no punchline, it is just "Saw". It's in theory extremely un-creative all things considered.
So there it is. The Joker is kinda white bread now. Which is a big problem, ESPECIALLY for a Batman bad guy since most of them are gimmick characters. Ventriloquist has his puppet, Riddler constantly tries to prove he is smarter than everyone else, Poison Ivy is obsessed with plants, Two-Face is crazy about duality, so on and so on. But when was the last time the Joker was funny? So he is just Batman's worst enemy since that is his role, no other reason.
That's all for now. Next time, why the Violator from the "Spawn" comics blows.