I would be quite curious to know how one classifies a piano teacher as 'the best piano teacher in the world/US/whatever'.
I mean what are the criteria? Is it for which students come out of them? So the teacher who produces the best soloists or the pianists with the more prominent career? Is it the one who provides excellent fundamentals of music? One who can offer a degree? One who is REALLY REALLY REALLY beautiful? etc...