Well, for starters, those two pictures are under very different lighting conditions! In the S4 picture, it's a bright day out so the lens is well illuminated. In the 930 picture, you're in a darkish room and the light source is actually behind you in the picture. That kind of light condition will definitely be less than ideal.
But the front camera on the 4s is probably better than the 930. You could probably get that just from looking at the specs. The Galaxy 4S front camera is 2Mp, and the Lumia 930's front camera is 1.2Mp.
How about pictures with the main camera? The Lumia 930's camera is vastly better than the Galaxy S4. You can see that too just from looking at the specs. Check it out:
Samsung Galaxy S4 vs Nokia Lumia 930 - Phone specs comparison