Most of the images in the D|S section are rendered with 3Delight, as Richard said, it is a question of plug-ins, shaders and postwork.
If you just load an item into the scene and render it like that, with the default lightning, you are sure to see a great difference with the promo images. Have a look at the DAZ-Forum or here to find some tutos on setting up the scene and lightning and using some free shaders.
Leaving the path of default settings will always get you better results!

Peter