Well, honestly, I think that there isn`t really a best pianist; music is too subjective. It`s not like math or science where everything is technical and has a straightforeward answer. But even then, there is a certain level of subjectivity. But if I had to pick a best pianist, I`d probably pick Sergei Rachmaninoff, because he has a mastery over his own pieces that no other pianist I know of has not ever attained. And about the eighth grade at seven years old. I honestly doubt that the person who says he did it really did, but I know for a fact that it`s possible. There was this genius who took piano lessons from the same teacher as me. Anyway, he`s currently attending medical school in Chicago right now at the age of 12. His name is Sho Yano and some of you have probably seen him on the news. Anyway, I just wanted to clarify that it is very possible to complete eighth grade at seven, though I doubt the person who said that truly did.

urmm.. I`m 16 now, I passed my FRSM last December..
It`s not impossible you know, I finished grade 8 when I was 12, did Associates when I was 13, Licentiate and so on till last year.. Did it all in the Royal School Board

well, in my opinion there is no BEST PIANIST but a lot of them, you can`t possibly name the top one as for example, their performance of Mozart might not be the best, while their performance of Schumann may be. A few of my FAVOURITE pianists:

Kissin
Argerich
Richter
Benedetti Michelangeli, etc, etc,

Well, if you want to talk speed then http://www.lubomyr.com/continuousmusic.html is the fastest, 19 notes per second with both hands isn`t bad ...

http://www.lubomyr.com/musik/LundSPS.mp3 there is a sample of one of the pieces he has written.