We have the richter scale, the scale that everyone knows. The one that said Haiti's earthquake had a magnitude of 7.0, and Chile's of 8.8. We also have the Mercalli intensity scale. The intensity scale takes into account the geology of the area and the independent effects felt by the earthquake at a particular location (from instrumental damage to catastrophic damage). Haiti felt a higher intensity (IX) whereas Chile experienced an intensity of VIII. Chilli is in the ring of fire, and they've got much more of a conciousness to earthquakes than Haiti. Their buildings were therefore built to strict building codes to prevent collapse during a 'quake, whereas Haiti has no building regulations. Earthquakes don't kill many people directly, buildings do. This could also be partly down to the wealth of the two countries.
There is also the knowledge that the earthquake that struck Haiti was a lot shallower than the Chillean earthquake, and much closer to a large populated town so Haiti was much closer to the epicentre.