Outstanding cast of characters. Not as good as Togashi's later work, Hunter X Hunter (due to some their backstories being just simple), but the characters, both protagonists and antagonists, are interesting and complex.
Great voice acting in both sub and dub.
The music theme song is very catchy and memorable.
Unlike most anime similar to this, there is absolutely no filler throughout the show.
Surprisingly great comedy.
Yusuke Urameshi's character arc is known for being one of the best and most engaging coming-of-age stories in all of anime.
Shockingly great romance between Yusuke Urameshi and Keiko Yukimura.
The villains in this anime are some of the most well known, interesting, and complex, in all of contemporary Shonen Jump anime and manga.
Excellent fight scenes.
All of the main cast have great dynamics together. Their interactions are always engaging, no matter what they're doing.
It has several unlikeable characters like the teachers of Sarayashiki High School who constantly bullied Yusuke and Kuwabara, or Gonzo Tarukane who was responsible for psychologically torturing Yukina to profit off her tears.
Yusuke's mother, Atsuko Urameshi, was a very useless character who contributed nothing for the anime.
Several characters were poorly underutilized in the anime like Chū, Rinku, Jin, Tōya, Shishiwakamaru and Suzuki.
Koto and Juri, while likeable characters, can be a little annoying.
It had some differences from the manga. The manga showed more realistic moments as an influence to Hans Ruedi Giger, and a notable example was that Mukuro was raped by a pedophile during her childhood and poured acid on herself in the manga, along with some characters not being in the show.