The big issue that's kept me from getting into western comics is the fact that most major ones tend to be tied to a major universe while manga are typically self contained. Sure, crossovers and such are good, but it's gotten to the point where there's several different series for some characters, and they all tie together. I don't want to read a bunch of different series for characters I'm not interested in to follow major events.

Then there's the fact that manga are allowed to have a conclusive ending while popular comics tend to go on for decades. And the fact that comics sometimes switch writers can create big inconsistencies in quality and style, and the decades of existing content and reboots creates a huge barrier of entry. I'm sure there are some great stories mixed in, and some standalone comics that avoid all this, but I wouldn't know where since I've avoided the medium as a result.