If you're interested in these types of things, there's a blog called
What Japan Thinks, which posts the results of market research surveys taken in Japan. According to
this survey ranking mangas, One Piece got the most votes for "manga that made you cry".
Most of the other titles on that list are probably unfamiliar to American readers, offhand I can recognize at least half a dozen which are over 30 years old and have no chance of being commercially translated. Further down you can read the results of a survey asking which manga people are most likely to recommend to others. One Piece tops the list again. Nodame Cantabile is at number six. ^_^
PS:
This survey about bad manners using chopsticks is also pretty interesting.