You know, there is something slightly sad about the fact that when it comes to "best manga" discussions and all, it's always Seinen (or sometime pseudo Seinen that are in fact Shonen) manga that are advanced and shown as best taste and all. I do get it when the vast majority of people say bersek and vagabond, etc etc , because they ARE indeed great/good manga.. but it also shown in my opinion that most people stay in the demographic that is aim for them, and are not curious enought to try other departement like shojo manga for exemple.
I think it's a problem, because personaly , I think staying in a confort demographic/genre zone only offer a narrow view of all the possibilities that manga can offer. One way to really realize that is when you actually go to japan and you see how much, in fact, the seinen/shonen manga that are by far the most praised, consumed and published manga in foreign country are in reality the minority when it comes to number in japan. Shojo manga litteraly crush them in term of publication and have such a wider range of thematic of genre you would usualy think. For one reason or another, all the shojo manga that are published outside of japan are 99% of the time school romance thing, and they are usually of low quality = this result in a depreciation of the departement as being filled with cliche and uninteresting tropes and all, when, in fact, and I assure you I'm not joking, the most psychologicaly violent and "hard to shallow" works I have read in my manga explorations were definitly shojo works. It really amuse me to see so much people talking about Berserk as being the most dark and mature manga that ever existed and using as reference, because, as funny as it sound, it's in shojo manga that there is the most death of important protagonist, suicide, rape, lethal accident, murder, etc.. All those things are actually super common in "true" shojo manga. And the funniest thing is that for a lot of them those story are intended to be read for young girls, not even adolescent let alone adults.
All that to say, that there is some huge misconception in the west about manga demographics, because we can actually only read the emerged part of the iceberg consisting of works that are supposed to appeal to us, and so are the only one published in other language. Why do you think the most interesting shojo manga are not published for us ? It's because in a sexist way to think, we would consider those works to be too graphically stange or "out of confort zone" and psychologically hard/difficult/violent for woman to enjoy. And so, most girl and woman that are invested and curious about manga as a form of art have to read Seinen works to escape the mellow insipid and graphicaly blank romance that are published for them. Really makes you think.
... I'm not even sure myself why I made this wall of text to defend shojo manga as it's not even my departement of predilection since like most people that posted here, I'm most interested in seinen works, but I guess all that bugged me too much and I had to get it out of my mind. haha
By the way, my personal and subjective trinity of best manga author are Inio Asano (Oyasumi Punpun/Umibe no Onnanoko) , Taiyou Matsumoto (Sunny/Gogo monster) and Kazuo Kamimura (Kantou Heiya/Dousei Jidai/Rikon club).
Edit: I think I should give some dark/mature/psychological/graphically inventive shojo manga exemple to back up what I said, before I might be asked to - Zankoku na kami ga shihai suru (and other works my Moto Hagio in general) , Banana Fish (currently being adapted in anime) , ES: eternal Sabbath (would recommend for people that like the famous manga "Monster" by Urasawa) , Kaoru Fujiwara's one shot manga (not one in particular, they are all very morbid) , Copernicus no Kokyuu (and the other yaoi rape fetish things the author like to make.. not my type of things to be honest).. and then I could give good shojo drama, but I'll stay with the more "dark" ones to show my points.
For those who prefer anime it seems like there is is very little actual Seinen made at all. Like above I mentioned Parasyte, which came out, I guess, like 3 or 4 years ago. Seems like there has been nothing since but badly animated new berserk. But there is endless amounts of stuff I am not interested in - school romance/comedy, overly 'edgy' shonen and mmorpg gamer crap :(
If anyone has any recommendations I'd like to hear them.