1) There's truly nothing like it anywhere else. Jhonen Vasquez's uniquely personal creation is a fusion of video game-inspired design, Lovecraftian monsters, 90s Goth (yeah yeah, he hates the term) aesthetic, Kafka-esque isolation, artistic insanity, and good ol' fashioned misanthropy.
2) Johnny is a compelling character. His persecution complex made him sympathetic to my younger self and increasingly frustrating to my older self. He's been the barometer I've used to measure my maturity, and I'm happy that the work remains compelling after all these years.
3) Johnny C.'s world is a fascinating place, all sharp angles and suburban decay. Massacres happen in grubby strip malls, decisions of life and death are debated over slurpee machines, bored Gothlings snipe at each other, and a cartoonishly cheerful sun smiles idiotically down on everyone.
4) There is a cohesive story underneath it all, with enough revealed to satisfy while still retaining the mystery necessary for Nny's world to function.
5) There's a real intelligence underpinning the material. Nny isn't a typical narcissistic serial killer in love with his inflated power fantasy. He's terribly fragile, terribly weak, and ultimately more pathetic than anything else. It makes what he does ultimately less glamorous. Most of his victims are cardboard-cutout morons, but the rare occasions Johnny converses with another intelligent, sensitive person shows just how pitiful his impotent rampages really are.
6) JtHM has an excellent supporting cast, from the malevolent Doughboys to the girls that get away, the people at the fringes of Nny's work as signifiers for the character's development. One of them even reveals herself to be a more psychologically stable version of Nny, and successfully overcomes the force that once enslaved him.
7) I got into JtHM at the same time I got into the Goth scene. I discovered the comic through Carpe Noctem, a dark arts magazine that Hot Topic used to sell. I've never entirely lost my love of the scene and revisiting Johnny the Homicidal Maniac feels like going home.
Conclusion: While I've outgrown a lot of the misanthropy that initially attracted me to the character, I've been really impressed by how well JtHM has held up over the years. It's still a unique and fascinating work by an extraordinarily talented young artist.