Since others have told me that this list has been helpful, I’m putting it up here. This list is not exhaustive, it’s not trying to lay out a canon, and it does not attempt some kind of suggested ‘course of watching’. It’s simply a handlist I’ve been compiling. For commentary on its construction, see this post. A few items (e.g. Lupin III) begin in one decade but last rather longer.
Before 1970
Benkei vs Ushiwaka
Hakujaden
Saiyuuki
Wanpaku Ouji no Orochi Taiji
Gulliver’s Travels beyond the Moon
Sabu and Ichi’s Detective Tales
Horus, Prince of the Sun
Flying Phantom Ship
1970s
Ashita no Joe
Animal Treasure Island
Hellhound Liner 0011
Aim for the Ace (1973)
All that Lupin III
A Poet’s Life
Heidi, Girl of the Alps
Space Battleship Yamato
Gamba no Bouken
Zambot 3
Future Boy Conan
Space Pirate Captain Harlock
Rose of Versailles
Aim for the Ace (1979)
Anne of Green Gables
Mobile Suit Gundam
1980s
Jarinko Chie
Gauche the Cellist
Armored Trooper Votoms
Arcadia of My Youth
Crusher Joe
Golgo 13: The Professional
Space Adventure Cobra (film)
Space Cobra (TV)
Dallos
Macross: Do You Remember Love?
Panzer World Galient
Fist of the North Star
Genmu Senki Leda
They Were 11
Toki no Étranger
Night on the Galactic Railroad
Windaria
Saint Seiya
Robot Carnival
Royal Space Force
Dirty Pair: Project Eden
Take the X Train
Black Magic M-66
The Golden Bird
Kimagure Orange Road
Bubblegum Crisis
MADOX-01
Mellowlink
Gunbuster
Patlabor, in its various forms
Dragon’s Heaven
Legend of the Galactic Heroes
Gosenzo-sama Banbanzai
Cyber City Oedo 808
Only Yesterday
1990s
Roujin Z
Goldfish Warning
Down Load
Giant Robo: The Day the Earth Stood Still
Dear Brother
Blazing Transfer Student
G Gundam
Macross Plus
Memories
Martian Successor Nadesico
Yume no Crayon Oukoku
Revolutionary Girl Utena
Infinite Ryvius
GaoGaiGar
Fun Fun Pharmacy
Jin-Roh
Medabots
Turn A Gundam
The Big O S1
Tenamonya Voyagers
2000s
Ojamajo Doremi
FLCL
Haré+Guu
Figure 17
Princess Areté
Crayon Shin-Chan: The Adult Empire Strikes Back
Mazinkaiser
Princess Tutu
A Tree of Palme
Godannar
Wolf’s Rain
Mind Game
Gankutsuou
Tetsujin 28-go (2004)
Windy Tales
Gag Manga Biyori
Noein
Kamichu
Pale Cocoon
Akagi
Simoun
Kemonozume
Oh! Edo Rocket
Mononoke
Dennou Coil
Kaiji
Manabi Straight
Guardian of the Sacred Spirit
Time of Eve
Mouryou no Hako
Michiko to Hatchin
Detroit Metal City
Shin Mazinger Z
House of Five Leaves
Princess Jellyfish
Cencoroll
2010s
Redline
Heartcatch Precure
The Idolmaster (2011)
Azazel-san
Jinsei Best 10
Hyouka
Tsuritama
Teekyuu
JoJo’s Bizarre Adventure
Turning Girls
Space Battleship Yamato 2199
Niji-iro Hotaru
From the New World
Gundam Build Fighters S1
Princess Kaguya
Eccentric Family
Pupipo
Yoyo and Nene
Shirobako
Ping Pong
Japan Animator Expo
Shashinkan
Gundam Thunderbolt: December Sky
Miss Hokusai
In This Corner of the World
Garo: Divine Flame
Doukyuusei
Baja’s Studio
Maquia
Pop Team Epic
Totsukuni no Shoujo
2020s
Akudama Drive
On-gaku
327 Robots 