A story should require the amount of chapters and volumes it needs to be enjoyable while still being about the main point. When a manga is filled with more side stories or stories about the supporting characters than there are chapters for the main story the manga should end relatively quickly. Ending it prematurely is also a nono for it leaves the reader unsatisfied and in worst case, enraged.
I prefer 5-15 volumes with 4-5 chapters for every volume with each chapter being 30-100 pages long. 10 Volumes, 5 chapters/volume, 60 pages/chapter is my exact preferred length, however, if the story require it, it can end before or after my preference.
It's different for 4-koma manga. For those I don't mind the length as long as it is still fun after 1 volume or a 100 volumes.

sorry can't vote because as long as it is a good manga and have the right ending i don't mind any of those choices

Last edited by En Do at 11:19 pm, Jan 29 2013

It really depends on the content of the story, how well written it is, and the style of the manga.

If it's cliche or a story that has been told before generally, short with a few volumes (or just one) is enough.

other than that, the other three options can do just fine as long as the story ends satisfactory.

So don't let people demean you and treat you like trash.