Personally, I like to just compare the distance on X and Y axes between the centerpoints of objects (their position in X and Y set as variables on the object, plus half the size of the object.. e.g. the centerpoint of a 32x32 object being object->pos_x + object->width*0.5,object->pos_y + object->height*0.5) .. with varying distances dictating whether a collision has occurred or not. The hit 'boxes' on my objects are NOT the same size as the objects, however. That works really well for the top-scrolling shooter engine I am developing; but it might not work as well for your application. You might give it a shot though.
