R.I.P. Ruben and thanks for your playing and personality.
As much as I like him, to put him in a league with Monk (a Cuban Monk, as Ry Cooder put it) does not show a deep knowledge of either Monk or Cuban music, and to call him the greatest Son pianist, is with all due respect, a little exaggerated. You have to put these names before him, and he would have been the first to admit this:
Peruchín (Pedro Justíz)
Luís Martinez (Lily Martinez, his predecessor in the Arsenio Rodriguez conjunto)
There is another one whose name escapes me right now.
These masters of Cuban music were late discoveries to the rest of the world, their "discovery" was overdue, and there are still more, dead and alive. That movie only scratched the surface, and only of Son, not even mentioning the other musical styles of Cuba - this is my main complaint about "Buena Vista Social Club".