Hugo Chavez was a lot of things. To some a hero, to some a villain. One thing cannot be denied, however; Chavez was the first to show that a left-wing leader in Latin America could be elected president, enact leftist policies to redistribute wealth and get re-elected multiple times.
Since Castro, the U.S. has tried to show that all leftists in Latin America are dictators intent on destroying civil and economic liberties. If put to a popular vote, most of these leaders would be thrown out. While Castro has in some ways lived up this reputation, if a left-wing leader got elected, like Allende in Chile, they met an untimely demise. In Nicaragua, Daniel Ortega took power as a revolutionary but with U.S. backing the Contras helped drive him from office, though officially he was defeated in an election.
While decrying the rights abrogated by left-wing governments, the U.S. backed right-wing dictators throughout the region who practiced oppression to a much greater degree. These leaders protected the interests of U.S. corporations, while enriching themselves and keeping the people in poverty.
Chavez ended the stereotype of left-wing leader as dictator. As someone who rose from being a peasant to being a leader, Chavez put in place policies to help the poor. He redistributed oil wealth to provide education and health care to those in need and won the loyalty of the majority of the country. Of course, these measures annoyed those that had benefitted under the old system. Chavez survived an attempted coup and two elections. HIs successes has led to other leaders like Lula in Brazil and Evo Morales in Bolivia getting elected. They are more moderate than Chavez and have enacted social reforms in their countries with a much smoother transition less upheaval. Would things have worked out as well without Chavez? Doubtfully.
Yes, Chavez was a bit of a megalomaniac and his centralization of power was, at times, excessive. However, it takes a larger-than-life character to make necessary changes. If a more progressive Latin America with less inequality is Chavez's legacy, then he made a positive impact on the world.