I'm not one to read manga, I'm very very picky with what I read. But so far of all I've read, nine times out of ten, it has a very unsatisfying ending. Sometimes it feels like the serial was loosing popularity during it's run and the editors cut it suddenly, causing the artist to rush the wrap up. And sometimes it feels like the artist has no idea how to progress the story anymore and just straight up ran out of ideas and just ends it suddenly. The worse are the ones that set up something really big but then suddenly end it without really explaining or going into that big something. And a lot of these mangas tend to be very LONG. Meaning they go on and on and on until you're questioning if any real progress is going to be made to the main "mystery" and thenn... nope.
I do like the manga system in japan though, as to how comics work in the west. Over there, and correct me if I'm wrong, an editor will give a story/artist a shot, either for one issue or a small story arch, and if it's rated well they will be allowed to continue the manga. You get manga that last YEARS going on and on and some which just end after a handful of issues. Because of supply and demand. It kinda feels like in the west, with Marvel and DC, that sort of competitiveness doesn't quite exist. But at the same time, this system of creating stories causes me to read great mangas with disappointing endings. Here's what I've read to show you what I mean:
Blame!, Billy Bat, I am a Hero, Homunculus (wow I thought I read more than that, am I missing some? I guess it feels like a lot because there's so LONG)