The earthquake in Haiti was 7.0 and the quake in Chile was 8.8. Doesn't really sound like much of a difference, does it? But if you look at the amount of energy released, the Chilean quake becomes absolutely staggering. The quake in Haiti released the energy equivalent of about 32 megatons, less than the 50 megatons of the Tzar Bomba. The quake in Chile on the other hand was about 15,800 megatons, about 6-1/2 times greater than the total current US nuclear weapons arsenal (about 2,330 megatons) and almost 500 times bigger than the Haitian quake.
There are a number of reasons why the Haiti quake was so much more ruinous: proximity to population centers, focal depth, terrain, etc, but the overwhelming poverty in Haiti was probably the biggest factor. Haiti is the poorest country in the Americas with a GDP per capita of only $790, while Chile is a G-20 member with a GDP per capita of $10,100.