1. Takehiko Inoue ( Vagabond )
2. Miura Kentarou ( Berserk, especially the last 25 volumes )
3. Kishimoto Masashi ( Naruto.. duh! )
5. Tite Kubo ( Bleach )
6. Takeshi Obata ( Hikaru no Go, Death Note )
7. Hiroaki Samura ( Blade of the Immortal )
Some of your list includes some really awesome artists I love. Like GK, I'm also an artist, so yeah.
Although my order's different XD
 Miura Kentarou (Berserk): Agreed. Last few volumes, he's improved so frikkin much, all the background scenes makes me cry. So pretty. XD Especially that ballroom scene. Zoom in on the deatils on the ceiling. Fucking awesome.
 Takehiko Inoue ( Vagabond ) / Hiroaki Samura ( Blade of the Immortal ): Haven't read them at all, but I have seen enough chapters and scenes from GK, to make me adore the artwork. That's what's making me wanting to read them now. Also, detailed artworks make me drool.
 Kentaro Yabuki (Black Cat) / Tite Kubo (Bleach) / Kishimoto Masashi (Naruto): Black Cat had the most amazing lines I've seen in a character. XD What I mean by that is how the hair, and face just looks so goddamn pretty. Especially the last few volumes. As for Bleach, the character designs and ideas are awesome. XD Same goes for Naruto. Original. ^_^
 Takeshi Obata ( Hikaru no Go, Death Note ): I've seen enough cleaned chapters by Knucky to make me like the artwork. ^_^
"Growing older is mandatory, growing up is optional."
These are my favourites in no particular order:
Eiichiro Oda (One Piece)
Tohru Fujisawa (GTO)
Takehiko Inoue (Slam Dunk, Vagabond)
Nobuhiro Watsuki (Rurouni Kenshin)
Tite Kubo (Bleach)
Akira Toriyama (Dragonball)
Takeshi Obata (Hikari no Go, Death Note)
Takeshi Konomi (PoT)
Hiroaki Samura (Blade of the Immortal)
Masashi Kishimoto (Naruto)
Tong Ai (Bowling King)
This is also pretty much the same order as my favorite mangas...I'm not gonna lie, the plot definitely has influence over my choices as favorite artists, so this list probably more closely is of my favorite mangakas...oh well.
I dont think i need to comment about Michelangelo, i mean he is michelangelo. I remember seeing some of his works in person in italy...omg, the sistine chapel is so much more impressive when it is right above you. I myself like Raphael especially his school of athens
I always love to talk about Michelangelo, in fact I did an exclusive study on all his pieces and his history last summer. That's awesome you got to see the Sistine Chapel. But this is the wrong topic to talk about him, tho - if you want to pursue the matter, we can start a thread about Fine Artists in General Discussion or Entertainment.
For me, I'd have to say Rumiko Takahashi. Sure, she doesn't know when to stop, and sure, her plots can become repetitive. But I still consider her a fantastic creator with a wonderful sense of humor and a great judgement of character. Her characters are flawed but likeable, and she always builds an impressive cast in each of her works. She is a very prolific manga-ka, having drawn nearly 150 volumes worth of manga, and she has written a story for nearly every genre save hard sci-fi (though she's done quite a bit of comedic sci-fi). My personal favorite works from her are her darker Inu-yasha and Mermaid Saga, which have very rich storytelling and folklore, though I also love Maison Ikkoku and Ranma 1/2 and many of her short stories.
Horrible? I can see why someone can become sick of something after 40-something volumes (if I wasn't way too forgiving, loyal, and patient for my own good I would have dropped it long ago) but I don't think it's necessarily become horrible. The recent chapters of Inu-yasha especially have some of the best character development I've seen in a shonen title for a very long time. Kagome especially becomes a very interesting heroine later on regarding her feelings towards Kikyo. But again I can see why alot of people hate Rumiko so I'm not about to debate about other's personal opinions.
Masakazu Katsura (I''s, Zetman, Video Girl Ai) draws everything extremely well Kubo Tite (Bleach, Zombie Powder) love his sense of style Shin Takahashi (SaiKano, Kimi no Kakera) very unique, almost scribbles Tsutomu Nihei (Blame!) can't beat this guy when it comes to skill, majored in architecture and it shows Takehiko Inoue (Vagabond, REAL, Slam Dunk) very 'complete' artist Nobuyuki Anzai (MÄR, Flame of Recca) tho not always very original, I love his facial expressions and character designs Oh! Great (Air Gear, Tenjou Tenge) gotta give it to the guy, his art is insane
Some additions to my list: Kentaro Yabuki [Black Cat, To-Love-Ru) lately I've fallen in love with the very stylish character designs of Black Cat, especially how he draws girls is very fine. It's obvious he was influenced by Toriyama, and mentored by Takeshi Obata. Yusuke Murata [Eyeshield 21] I don't think anyone can draw better action scenes that portray the energy American Football is all about, very dynamic stuff, good clean style overall Makoto Yukimura [Planetes, Vinland Saga] Just an incredibly talented guy in every aspect, I can't find any faults in his artwork, facial expressions are really distinct Yoshiyuki Sadamoto [Evangelion] Very classic character design, in a modern way. Wish he drew more manga in his career. Ken Akamatsu [Love Hina, Negima!] Though he's got a huge team working with him now, I've always loved how he draws girls. Fanservice-wise he knows his stuff. Akira Toriyama, cant believe I didnt mention him before, his early Dragonball artwork just reeks of pure fun. Very distinct comic style with crazy imagination all over the place. Hideo Yamamoto [Homunculus, Koroshiya Ichi] I don't think anyone is more suited to portraying the ugly side of mankind. A lot of his stuff relies on visual storytelling, which I always love. Hitoshi Ashinano [Yokohama Kaidashi Kikou] Just looking at his drawings in YKK makes me relax. Cute character designs and expressions too. Yuki Urushibara [Mushishi] as artistically beautifull as it can get. The amount of time spent thinking up all of those mythical beings is amazing. Minoru Furuya [Ping Pong Club, Ciguatera] It still baffles me how much he has grown as an artist AND a storyteller. Another person who is great at drawing the darkly cynical side to humans. Hilarious expressions.