We tend to think of a "good Samaritan" as being an exceptionally helpful person--even to a stranger, perhaps--and that is not entirely wrong. But there is really more to the matter than just that.
The Samaritans had allied themselves against the Seleucids, and fought a war against the Jews. This certainly did not endear them to the Jewish people.
Also, a group of Samaritans once profaned the Temple by scattering the bones of dead people in its sanctuary.
Moreover, the Samaritans had intermarried a great deal over the generations--they were part Jewish and part Gentile (or what nineteenth-century Americans might have referred to as "half-breeds")--so the prejudice against them was even greater.
The apostle Paul would later speak to this when he wrote that there is no such division between "Jews" and "Gentiles." But in first-century Israel, a Samaritan was about as low on the totem pole as one might possibly be.
So to be a good Samaritan was not merely to be exceptionally helpful. Rather, it was to imply the question (actually asked by Jesus): Is your true brother this priest (who passed you by); or this Levite (who also passed you by); or this Samaritan (who actually rendered aid)?
A more deeply ethical point, I simply cannot imagine.