I'm sure that a similar survey was done not a long time ago. Anyway the survey was for the most "omoshiroi" manga: omoshiroi meaning a number of things from interesting to curiousity-perking to amusing, and I think the responses are quite appropriate.
And I'm amazed at thatbabo's list... The US has a rather polarized manga audience it seems. I like Naruto, but 7 out of the top 10 is just weird.