But quality vs quality aside, has Moebius done anything that's as gigantic, mythic, and poignant as the New Gods? Kirby pretty much created an entire mythology that speaks to the nuances of our current era.
Kirby was an unrivaled "ideas" man in comics, but even in his most prolific period, he had developed his default style and didn't play around with his storytelling all that much. (Quite frankly, he didn't have to-- it always worked.) It's undeniably incredible (and important) work, but it's also fits very squarely within a certain template for action/adventure stories.
Sim, crazy as he is, continually experimented with his storytelling, really pushing what you can do with sequential art. What makes those 300 issues of Cerebus remarkable is that he rarely repeats what he's doing-- it doesn't always work, particularly in the last 100 issues, but there's still this effort to expand and experiment with how he's telling the story.
Now, I think the argument that can be made was that Kirby was primarily working to entertain children, and his work reflects that aesthetic-- it's big, it's powerful, and it's relatively easy to follow. Sim was working to entertain an older audience, one that had grown up with comics and wanted something more sophisticated than big action scenes. Sim takes Kirby as channeled through Barry Windsor-Smith as his starting point and moves in an entirely different direction, evolving his storytelling as the story he's telling grows beyond an action/adventure story.
Both are excellent, and both created extremely important works for the medium. I don't think they were doing the same thing. There's no denying Kirby's impact on the American superhero comic or even the action/adventure comic in general, but when you branch out from those kinds of stories or out of the Anglophonic market, his influence isn't quite as present.
He's loved all over the world, has had his own exhibition, had a shared exhibition with Hayao Miyazaki (they're best pals and Nausicaš is SO heavily influenced by Moebius and Moebius named his daughter Nausicaš) and is considered the one of FINEST comic artists in the world.
EDIT: One of the co-creators of Heavy Metal
It's an extraordinary picture in its design and dynamism. It has movement and energy. It's genuine comic book art. Batman is punching a guy in the face, and thanks to the motion line you can actually imagine the arc of his arm gaining balance to hit him harder. This motion line helps give the illusion of movement in the picture. That illusion is also aided by the neat touch of having the hat fly off with the impact; sure it's exaggerated, but it communicates information better that way. Also remarkable is the electric-yellow background, lighting up with the impact of the punch to emphasize its strength. And Batman is punching him from left to right, as our Western eyes would expect, respecting the most basic of visual storytelling rules. It's perfect for what it's meant to accomplish.
This, by comparison, isn't very good:
(Steve Epting, Captain America v.5 #26)
In the first panel there's no sense that Bucky is using any strength in his fists, no illusion that his arm is moving across the air; that's because Epting is too incompetent to use motion lines. The figures are also so far away from each other you can't even believe his arm hit the guy; if he wanted to transmit the idea the guy was being pushed back by the impact, Epting failed because he didn't add any motion or impact lines to transmit the idea of energy, strength and movement. It's just a still figure, it could easily be the cover of a book or an illustration.
In the second panel we have Bucky bizarrely striking the air when his opponents are all far away from him. This man is supposed to be a professional fighter? The art doesn't show that.
There's no continuity between panels two and three. In the second panel Bucky is stupidly opening his defenses, exposing himself, and allowing his rear guard open to a guy with a stick to hit him; strangely that figure disappears and Bucky is next seen punching someone else. Needless to say the punch in the third panel lacks any impetus, any sense of force or movement because, again, Epting never heard of motion lines. It's just two figures who look more like they're choreographing a harmless ballet dance than actually having a bar brawl.
By comparison, Kirby's fight sequence:
And the motion lines, this is a textbook example of how to use them to create the illusion of dynamism. I believe these characters are moving, I believe their punches and kicks are full of strength and agility. When characters are moving, you show them moving! Then, for contrast, in the final page, when the fight is over, look at the stillness, no motion lines. Sheer brilliance of design.
Most comic book artists nowadays don't know how to draw comics; they know how to draw pin ups, book covers, wall posters and playing cards, and somehow they've fooled buyers into thinking that's actual comic book art. It's not. Kirby drew comics. People like Epting (and sometimes Moebius too, especially in Arzarch) drew illustrations.