Briefly:
Nausicaa - Briliant ecological fable courtesy of Hayao "Love Me" Miyazaki. This, friends, is what manga can be when it tries.
Planetes - Near-future hard science fiction about the poor bastards who have to clean up space debris in orbit. The characterization is simply astounding. Crucial reading.
Lone Wolf and Cub - Violent, highly influential 70s samurai saga; Blade of the Immortal ain't bad, but be sure you read this first.
Five Star Stories - Epic, intricate, non-linear insanity from Mamoru Nagano. This is drop dead gorgeous stuff; just flip through a volume and see for yourself.
Maison Ikkoku - The gold standard for romantic comedy. There's not a single high school student to be seen, plots often involve heavy drinking, and it captures early-80s Tokyo perfectly.
Crayon Shin-chan - Wacky gag comics about a naughty little boy who tries to be more mature than he really is. Learn what "Buri Buri" means! Meet "Mr. Elephant"! Watch Shin-chan hit on women! It's a hoot and a half.
Phoenix - Osamu "God of Motherfuckin' Manga" Tezuka's masterwork, a series of humanistic fables set in different times and centering on the continuous reincarnation of the wondrous Phoenix. Brilliant, particularly later volumes.
Buddha - Tezuka does
Siddhartha. More fantastic material from the man during his 70s peak.
And, from the Shoujo-Is-Good-For-You Dept(tm):
Please Save My Earth - Reincarnated aliens with psychic powers, angst, and plenty of romance. I rave about it in detail
in this thread.
Banana Fish - Clean art and harsh storytelling combine in this story of drugs and rival gangs in early 80s NYC. It also has pretty boys in love; if that ain't your thing, don't worry, the rest of the series is so badass you won't even notice.
Four Shoujo Stories - Three of which are pretty good and the fourth, "They Were 11", is freakin' astounding. 70s gender-bending SF (think
The Left Hand Of Darkness) meets murder mystery. Classic.
FnordChan
