The problem with shorter manga is that the bulk of it falls thus:

1) Meant to be a huge, epic thing but didn't sell well so it got cancelled with a sloppy ending.

2) Meant to be only a few chapters but got popular and was made longer, but didn't have the story to maintain it's length.

There are, though, a fair number that are as long as they're meant to be. A lot of them tend to be rather light reads because the length doesn't allow for much deep development long the longer series do.