What makes an art "good" can vary depending on your taste, so I'm going by my personal taste here:
Stylized:
Satoru Noda (Golden Kamuy)
Akihito Tsukushi (Made in Abyss)
CLAMP (Cardcaptor Sakura, Tsubasa Reservoir Chronicles, xxxHolic)
Eiichiro Oda (One Piece)
Kohei Horikoshi (MHA)
Posuka Demizu (The Promised Neverland)
Saeki Shun (Early days of Shokugeki no Soma)
Anatomical:
Boichi (Sun-Ken Rock, Origin, Dr. Stone)
Hirohiko Araki (JoJo's Bizzare Adventure)
Junji Ito (horror mangas)
Kaoru Mori (Otoyomegatari)
Katsuhiro Otomo (AKIRA)
Kentaro Miura (Berserk)
Makoto Yukimura (Vinland Saga)
Masashi Tanaka (GON)
Masasumi Kakizaki (RAINBOW)
Oh! great / Ogure Ito (Air Gear, Bakemonogatari)
Q Hayashida (Dorohedoro)
Shinichi Sakamoto (Innocent, Innocent Rogue)
Takehiko Inoue (REAL, Slam Dunk, Vagabond)
Tsutomu Nihei (Blame!, Knoights of Sidonia)
Yuusuke Murata (Eyeshield 21, One Punch Man)