We get this so much in the comics thread, I find it so odd. Reading 'all' of Batman or Cap is a fools errand - for starters, most of it will be pretty bad. As I say, it's not that the books go on forever at all - there are runs within the series that are complete and satisfying reads. For instance, you could read all of Brubaker's run on Cap and get a massive, sprawling and complete story. Or you could read Remender's current run. They're often informed by the past, but it's really just context, the runs themselves are nearly always complete within themselves.
Things like art styles are subjective of course, but it's not all rippling muscle and grimaces. The Brubaker run on Cap has some really great heavy-brush style art throughout the run, very grounded and well proportioned. Both sides have their strengths and weaknesses - manga has unparalleled senses of speed and movement, and the background work is often incredible technical drawing (Akira still blows my mind with the environment design). But the style is fairly homogenous and IMO fairly odd in the ways that they go about drawing Japanese people.
Western comics have a broader scope of styles available to choose from, and I don't think there's anything in manga similar to someone like JH Williams who is able to play so much with the form of narrative storytelling
Another interesting thing that comics have that is (probably) unique to all of media is these massive collaborative universes that are a feat of accomplishment in and of themselves. Added to by hundreds, thousands of minds over the years, staggeringly complex at times and yet mostly cohesive and accessible. The feeling of history and continuity is unmatched in any other form of storytelling.
Also, I think it's important to note the cultural aspects of being a westerner who is primarily a manga reader. Often times these folks are into lots of other Japanese media too, games, anime, music etc. These people have chosen to immerse themselves in a fairly alien culture and to define themselves pop-culturally through that. In which case it's not really surprising that they don't jive with more traditionally western artforms.