He stood up to American bullying, and he did it with flair and intelligence. Who does not admire the little guy who stands up to bullying?
American interests in Cuba had been to a great extent gambling, nightclubs, prostitution, and other dark activities. Castro did largely end this, making an enemy of the American Mafia interests who owned what had been goldmines.He rescued his nation from being an off-shore dyonisian playground where US citizens from the bible belt states could hide their sins from their neighbours. Walking off a ship in Havana now, one no longer has to run the gauntlet of a long avenue of brothels. It remains to be seen if his brother Raul can set his free people from himself whilst keeping them from being enslaved (again) by US dollars.
Castro did genuinely try to help his people, and he did some very worthwhile things.
In Cuba, a poor country, the average 8th grader is better educated, by far, than he or she is in the United States. Tests and observations have shown this many times. His health care system and medical training were remarkable achievements. Both recognised by the UN and the World BAnk.
He resisted numerous murder attempts by the CIA and its agents, he resisted an invasion, and he withstood a senseless embargo.
These facts tell us something about Castro not widely appreciated in the U.S. and some countries in Europe. He was a popular figure despite having opponents just as all politicians do.
Castro's only flaw was that of all dictators, he wouldn't hand over power. Like most "communist" dictators he found out that the latter part of Marxism, the withering away of the power of the state, will never happen in human society.