Well, the "original" is basically like looking through the viewfinder of a camera and the final shot can have a lot of things to make it look of a lower quality. Primary of them is it being blurry either caused by camera shake (either due to movement of the iPhone usually caused by not holding it securely, the way you "tap" the shutter button or subject movement if the light is not perfect). Now if you are seeing noticeably lower quality in good light - where the iPhones excel - then there might be something wrong with the iPhone itself. Because in good light, most of the problems I pointed out should not have as big an effect on the final image.