From the little I remember from school, he was charismatic and pretty progressive for his time. He was a supporter of the Civil Rights movement, partly responsible for the passage of the Civil Rights Act. He was committed to an aggressive space program, established the Peace Corps, etc. He also had a messy personal life with multiple extramarital affairs.

His nephew (RFK Jr), who is currently running for president, should not be viewed as the second coming of JFK. They are 2 very different people, which may be a good or bad thing depending on your political beliefs.