Manga reaches higher heights more often than western comics because it is allowed to reach deeper depths. Manga is a pulp medium, where material is cranked out at an incredible rate (often a chapter a week, with 20 page chapters) by the same author over the course of years, with relatively little oversight.

Because it’s seen as cheap trash (and individual series, unless they are extremely popular, are disposable) there’s a freedom to experiment, and the strange requirements unique to manga produce pressures that can result naturally in decisions that seem like strange formal experiments.

(As a fictional illustration of this, look at the throwaway gag in Weekly Girls Nozaki-kun wherein the title character, a shoujo manga author, doesn’t keep track of settings — drawn by another artist — and therefore produces strange perspective problems when drawing the characters. Because of looming deadlines, he tries to avoid needing to redraw every frame by having characters stand on boxes. This is rejected by his editor as a stupid idea, but important elements in landmark manga series have sometimes come from similar situations. The strange mix of martial arts and references to western action films in Dragon Ball come from frustrations the author had in coming up with inspiration for his previous gag series; no doubt Otomo’s tendency to name villains in Jojo after western musical acts comes from the same pressure.)

Because it’s seen as cheap trash, manga has also been used historically to cover material that would be seen as scandalous in more ‘serious’ works.

For instance, in the 70s feminist ideas were censored by Japanese publishers in much the same way they are currently censored by Russian publishers, with much the same rationale (that feminism is some kind of western psyop intended to sap and impurify the masculine essence of the fatherland or something). Shoujo manga magazines didn’t bother to censor feminist themes or feminist ideas when they were encoded into the subtext of stories, and so shoujo manga (which was considered even cheaper and crappier than shounen manga at the time, and thus worthy of even less consideration) became the primary medium for discussing ideas about gender and power relations. Because shoujo was really producing new stories full of ideas that were mostly novel to the audience, young people (especially college-aged men who wanted to go into writing manga) got really into reading and writing 70s shoujo manga that played with gender roles and gender identity, and a lot of those people later became influential in their own right in other genres, so we can almost directly credit the fact that money men in the 70s thought manga was trash with the widespread presence of traps & androgynous characters in modern anime.

A real boon to the high status of manga in the west is that we don’t import the trash. We only ever see series that are somewhat successful.

Now, there’s a subset of western comics that mimics some of what manga does, in a way that produces slightly more consistent results. This is the kind of semi-independent single-author-run miniseries that we associate with Grant Morrison, Alan Moore, and Neil Gaiman. Stuff like Watchmen, Planetary, and The Filth is allowed to be radically experimental because it doesn’t contain any characters from the wider universe and so negotiations with other authors is unnecessary; stuff like The Dark Knight Returns and The Killing Joke, while containing characters from the wider universe, is isolated from canon in some ways (TDKR is not canon; TKJ canonically paralyzed Barbara Gordon but Wayne’s heavily implied mental break & face-heel-turn is ignored). These also have other benefits: they are self-contained (like most anime but unlike most manga, they have a target end date, which makes tight storytelling possible), and monthly or bi-monthly release of issues means that more work can go into each (including color). However, there are certainly notable failures: The Dark Knight Strikes Again failed on pretty much every level, The Invisibles is great but heavily flawed because of story structure problems early in the run & inconsistent art quality, and even from the luminaries I’ve mentioned nearly all of their works are not well-known or necessarily respected. On top of that, every notable author who does this (1) is a white dude who started doing it while working for DC or Marvel in the late 80s, and (2) is from the UK (with the exception of one). Fewer than ten guys are making this work, and all of them have the backing of the same organization that pumps out twelve mediocre batman comics a week.

There’s another issue that complicates matters, which is that the differences between manga and western comics are mostly related to business structure. I’ve been primarily comparing manga that get US trade/tankoban releases to comics that get US weekly book distribution, but the stuff that gets US tankobans is often more comparable to what in the US would be considered indie comics (i.e., not released under a Marvel or DC imprint) and sometimes is close to what would be considered underground comix (i.e., small-batch fully-independent distribution catering primarily to the fringe and supporting risque contents: anything coming out of a doujinshi circle, whether or not it’s attached to a franchise, is going to be like this, aside from ascended doujin circles like CLAMP who are now part of the industry).

There’s actually a rough manga equivalent to DC in the form of Shounen Jump, which focuses on extremely long-running action-centered manga and sometimes flexes its muscles in affecting anime adaptations of its franchises. It puts out relatively few series compared to the general domain of manga available but it’s by far the most popular manga magazine & its highest-ranked series also dominate tankoban sales in japan (and probably abroad as well).

But, there’s a difference here in that basically every american comic that shows up in japan or gets heavy advertising in the US is owned by DC or Marvel. (The total distribution, not weighed by popularity, probably actually favors black and white indie comics in the west too, but you’d never know it by a visit to your local comic book store.) The reverse isn’t true: while Shonen Jump titles are very popular, most of that popularity is concentrated on the top four or five (One Piece, My Hero Academia, and as of a couple years ago Naruto and Bleach), and long-running popular Jump titles that never got anime adaptations are largely unknown in the west; furthermore, most of the manga we see on store shelves were serialized in less popular magazines.

There’s definitely a ‘house style’ — a set of tendencies resulting from institutional pressures — that characterizes the most popular Jump titles, the same way as there is for DC: Jump titles tend to be long-running, violent, and have simple/cartoony character designs with protagonists who are shorter than the people around them; often, the protagonist is an underdog who has a rival who is a childhood friend. This is exactly the kind of sameness that having a variety of lower-distribution magazines solves: manga would not be so popular in the west if most of it was Jump.

EDIT: I can’t keep Frank Miller’s Batman trades straight.