Because he is the perfect foil for Batman. He's the Yin to Batman's Yang, his complete opposite in every way. And, occasionally he actually can be quite funny, and yet creepy and scary at the same time.
Because the character's flexible nature meant that it was very hard to write a bad story for him: he was a great, dead-series pulp villain in the 40's, a silly and comedic mastermind in the 50s, a cunning and colorful adversary in the 60s and 70s, a sometimes funny, sometimes disconcerting portrait of madness in the 80s, personal foe in the 90s, and monster in the 00s.
I mean, look at the staying power he had compared to other villains. He's as old as Catwoman, and there wasn't really any time where he ever faded into the background, like Two Face in the Silver Age or Scarecrow before his gas attack or Riddler in the late 90s. Because he could be anything from funny to scary, he never went out of vogue.
And I think that lead to him getting the trio of 80s stories that cemented his comic status as the arch villain over even Ra's: he was the iconic rogue at the end of DKR's first half, part of Alan Moore's revolutionary GN Killing Joke (which I found boring and a little aggravating but is kind of astounding in just how modern it is), and Death in the Family. With a resume like that, he made perfect sense as the villain to help launch the film series, and that continued to bolster his fan power.
Ra's Al Ghul was arguably a bigger, more important and more exciting foe for a while after he premiered. Riddler was the most popular villain from the TV series. Bane dominated the 1990s. But Joker has a classic story in pretty much each decade since his appearance, and even with resurrections and reboots, has a grisly and personal tally against Batman and his family.
And his media appearances are pretty much unparalleled. Cesar Romero's the only cinematic actor for the character without an Oscar, and Cesar Romero was still a reeeaaallly good actor. Mark Hamill, meanwhile, has become a major league villain voice actor, and Joker's easily his most famous voice work. The character's been a major villain in literature, movies, video games, cartoons and live action TV (heck, the Hamill-voiced cameo in Birds of Prey is sometimes the only reason people have even seen that show.)
He's the most exposed and successfully performed supervillain in comic history.
Never truly being defeated!!
Because the character's flexible nature meant that it was very hard to write a bad story for him: he was a great, dead-series pulp villain in the 40's, a silly and comedic mastermind in the 50s, a cunning and colorful adversary in the 60s and 70s, a sometimes funny, sometimes disconcerting portrait of madness in the 80s, personal foe in the 90s, and monster in the 00s.
I mean, look at the staying power he had compared to other villains. He's as old as Catwoman, and there wasn't really any time where he ever faded into the background, like Two Face in the Silver Age or Scarecrow before his gas attack or Riddler in the late 90s. Because he could be anything from funny to scary, he never went out of vogue.
And I think that lead to him getting the trio of 80s stories that cemented his comic status as the arch villain over even Ra's: he was the iconic rogue at the end of DKR's first half, part of Alan Moore's revolutionary GN Killing Joke (which I found boring and a little aggravating but is kind of astounding in just how modern it is), and Death in the Family. With a resume like that, he made perfect sense as the villain to help launch the film series, and that continued to bolster his fan power.
Ra's Al Ghul was arguably a bigger, more important and more exciting foe for a while after he premiered. Riddler was the most popular villain from the TV series. Bane dominated the 1990s. But Joker has a classic story in pretty much each decade since his appearance, and even with resurrections and reboots, has a grisly and personal tally against Batman and his family.
And his media appearances are pretty much unparalleled. Cesar Romero's the only cinematic actor for the character without an Oscar, and Cesar Romero was still a reeeaaallly good actor. Mark Hamill, meanwhile, has become a major league villain voice actor, and Joker's easily his most famous voice work. The character's been a major villain in literature, movies, video games, cartoons and live action TV (heck, the Hamill-voiced cameo in Birds of Prey is sometimes the only reason people have even seen that show.)
He's the most exposed and successfully performed supervillain in comic history.
Joker is a great character but he's generally overused. There is a wealth of great villains to utilize in Batman stories that have not been given their proper due in various ways. Overexposing Joker hurts the character in my opinion. He ceases to be much of an unpredictable force of nature when he's showing up all the time. Better to withhold and bring him into a story only when its needed. Makes his presence have more of an impact.