Comics, as far as I know(I don't read comics much so tell me if I'm wrong), have a bunch of different stories/timelines. For example if I were to read a Batman story, then move on to read another Batman story(let's assume they're both canon), there's a good chance both of those stories have absolutely nothing to do with each other and probably happens in some different universe. I got that idea from that one time Batman took out the entire JLA when he first met them a long time ago, but I don't think that actually ever happened. Batman right now in Batman new 52 I doubt could be able to go to Superman and say "lololol remember when I whooped everyone in the JLA when we first met?" Cause I think maybe that was just a mini story. Manga is a long continuous story and it's easier to keep up with.
Like I said I don't read comics but they're weird to me, let me stress that I'm basing this off of small things I've seen without context. Maybe I'm completely wrong and they're exactly like manga. But idk.