I was often asked by friends of the pianists I like. On the other hand, some would be interested in those I don't like. As I have an avid interest in pianists, I've devised, for convenience's sake, a classification system of my own called none other than AVID.
'A' is for those I simply adore. 'V' is for those I value much, 'I' for those I feel indifferent to and 'D' for those that are disappointing or those I even despise. Simple enough. At least it serves me right up to this moment.
Here is my very personal list from memory:
A: (in alphabetical order)
Sviatoslav Richter, and
V: (in alphabetical order)
Emil von Sauer,
and a few others.
Don't force me to disclose.
There must be some pianists that I don't know, but I suppose I've known quite a number of pianists from the 19th century till now that I can make an informed choice. That's the reason that many notable names are absent, or at least not revealed, in my list. Such a list is useful to me in housekeeping for my collection which has been scattered among different places.