please see this 7 Years old video done with Unity3D:

The features from this Scene are:
- precomputed atmospheric scattering above the clouds
- ray marched procedural volumetric clouds with multiple forward scattering
- ray marched atmospheric scattering and procedural volumetric fog below the clouds, lit by the sun and the sky above
- directional ambient lighting for diffuse surfaces using dynamically updated spherical harmonics
- reflections for smooth and rough specular surfaces using a dynamic environment map

Is it possible to make such a good looking Scene with the Unreal Engine 4 today? Sorry, but in my opinion it's not possible!

If i'm wrong, and you can do something like this, please show me your Results here!!!

Many Thanks!