What are the best seinen mangas?

Vinland Saga (Vol. 1) is a manga by Makoto Yukimura. Seeking for revenge, Thorfinn was raised by Vikings and became a warrior to find justice for his family. 

Naoki Urusawa's Monster (Vol. 1) is a manga thriller. Brilliant doctor Kenzo Tenma risks his reputation and promising career to save the life of a critically wounded young boy. Unbeknownst to him, this child is destined for a terrible fate.

Parasyte (Vol. 1)  is a horror manga written and illustrated by Iwaaki Hitoshi. It is about the high school boy Shin, who found out that a race of parasites has taken over a large number of people in his town.

Akira (Vol. 1) is a science fiction manga by Katsuhiro Otomo. Set in 2019 after Tokyo was destroyed by World War II, two teenage friends Tetsuo and Kaneda fight against a monstrous power known as Akira. 

Gantz (Vol. 1) is a manga by Hiroya Oku. It is about Kei and Masaru who was struck by a train after saving the life of a drunkard. But mystery starts when they are still alive after the accident and became members of an organization called Gantz. 

Hellsing is a manga by Kohta Hirano. It is translated by Duane Johnson and Wilbert Lacuna. It is about an organization tasked to defend England's queen against vampires, witches, and other dark forces.

A Bride's Story Vol. 1 is a historical manga written by Kaoru Mori and translated by William Flanagan. Originally published in 2009, it focuses on Amir Halgal as she struggles to cope with the cultural differences with her husband.

Blame Vol. 1 is a space opera comic book series written and illustrated by Tsutomu Nihei. First published by Tokyopop in August 2005, the Blame series was released by Polygon picture as an anime film adaptation via Netflix.

Battle Royale Nook 1 is a dystopian manga thriller written by Koushun Takami and Masayuki Taguchi. Originally published in 2000, it is adapted in English by Keith Giffen and translated by Tomo Iwo.

A Drifting Life is a gekiga manga written and illustrated by the legendary Japanese mangaka Yoshihiro Tatsumi. This slice of life and drama graphic novel was originally published in 2008. It has a 2011 film adaptation entitled Tatsumi.

Wolf's Rain is an action-adventure manga written by Keiko Nobumoto and illustrated by Toshitsugu Iida. This manga has an anime adaptation with 30 episodes released in 2003-2004. Wolf's Rain has 2 published volumes.

Shirahime Syo: Snow Goddess Tales is a supernatural fiction written and illustrated by a group of mangakas called Clamp. This manga is composed of 3 short stories featuring a man's encounter with a snow goddess.

The Drops of God is a manga about wine created by Tadashi Agi and illustrated by Shu Okimoto. This sequential art manga is about the competition of two adoptive brothers for the wine collection. 

Good-Bye is a collection of gekiga stories written and illustrated by Japanese cartoonist Yoshihiro Tatsumi. This graphic novel contains all the nine works produced by Yoshihiro in 1971 to 1972.

Fallen Words is a historical fiction gekiga manga written and illustrated by Japanese cartoonist, Yoshihiro Tatsumi. This graphic novel was originally published in 2009. Fallen Words explores the oral tradition of rakugo through visual art.