Well i haven't watched Astro Boy either but it is a classic lol..... The rest i have actually seen. Inuyasha was my first anime
Tbh, rather than talking about what the classics already are, wouldn't it be more fun to discuss what newer series will turn into classics in the future? After all, everyone already knows the classics. I'd suggest something like Steins; Gate. Or has that already become considered as a classic?
Steins; Gate is amazing, but not known enough neither everybody likes it. Actually many people find it boring. xD
Mangas: Osamu Tezuka's works (ie: Kimba, Astro Boy, Black Jack, etc), Ranma 1/2, Urusei Yatsura, Slam Dunk, 3x3 Eyes, City Hunter, Gunsmith Cats, Saint Seiya, Hokuto no Ken, Akira, Gunnm, Patlabor, Kyoushoku Soukou Guyver, GS Mikami, Ushio to Tora, Zenki, Jigoku Sensei Nube, Flame of Recca, Yuu Yuu Hakusho, Doraemon, Ninja Hattori, Glass Mask, Haikara-san ga Tooru Anime (all above has already got their anime ver, so I'll just list something else. Some of the series are also got their remake in '90 and/or live action): Go Nagai's works (ie: Mazinger, Great Mazinger, Grendizer, Getter Robo, Kotetsu JEEG, etc), Voltus V, Dancouga, Cyborg 009, Macross ('82), Mach GoGoGo, Gatchaman ('72), Casshern, Hurricane Polymar, Time Bokan series, Uchuu Senkan Yamato, Gaiking ('76), Tetsujin 28, Babel Nisei, Galaxy Express 999, Captain Harlock, Queen Emeraldas, Gundam (any pre year 2000 series), Tekkaman Blade
Anime that made my childhood: One Piece Hunter x Hunter (1999 version but I saw also all the 2011 version that kind of seems lacking something but is pretty good) Glass no Kamen (1984 version but I also saw the 2005 one and it's more complete) Dragon Ball Lady Oscar Captain Tsubasa (Holly and Benji) These are real classics for me, I watched them even before knowing what was an "anime" ^-^
Feeling nostalgic 本気(read as maji) by Tachihara Ayumi - old fashioned gangster manga of old, romance, bad guy, good girl, tragedy but not.
Dragon Ball, One Piece, Rurouni Kenshin, Yu yu Hakusho, Inuyasha, Death Note, Ouran high school host club, Card captor Sakura, Naruto, Bleach, The wallflower, Black Butler, Hana yori dango, Glass mask, Ranma 1/2, Inuyasha, Yuyu Hakusho, Slam dunk, Toriko, Gintama, and Hunter x Hunter.
if we went by actual classics then legend of the galactic heroes could be considered one of the best classics in existence!!! if we are talking about favourite anime that could potentially become classics in the future i have a few such as; Jormungand (one of my all time favourites), Fate Stay/Nigh Unlimited Blade Works, Fate/Zero (one of my all time favourites), Code Geass (probably can be considered a classic since it is over a decade old), Death Note (the anime that brought about half of the community to start watching anime), Full Metal Alchemist: Brotherhood (one of the classics for sure, since it usually is within top 5 of all anime)...