I was thinking about this and I offer some thoughts…
If we look back to the beginning of the 1960s, Castro and JFK were both successful for a few of the same reasons…they inspired the younger generation of their respective countries with their youth and political visions.
(And as a meaningless coincidence, both had brothers that wanted to follow them in power.)

Sadly, we know what happened to JFK. They say American youth were turned off of government by Vietnam (which Kennedy’s political heir escalated byong all recognition of the original goals for South Vietnam) and Watergate. (I don’t entirely agree with this conventional wisdom, there are lots of active young people on both sides of the political spectrum.)
Today, some media types are now breathlessly comparing Obama to JFK in his ability to inspire a new generation.

But what about Castro? He hasn’t been able to inspire a new generation of communist revolutionaries despite considerable efforts in Africa and South America. Now he’s an old man and reluctantly passing power to his slightly younger brother.