Quote - I believe that I started the thread with the wrong words. I was asking if it was possible with Vue to make images like Mopplewilli's, which "happen" to be made with Terragen, not that I was looking for the Terragen "look".

Then the title of this thread should have been how to make more realistic terrains with Vue.  Sorry, I misunderstood your question.

Quote - In more generic terms the question was, can Vue generate totally realistic images without the children-illustrations look that is characteristic of the program.

Vue can indeed produce very vivid, "non-childlike", realism.  The keys IMO are getting the lighting/atmo set up properly and using decent materials/textures.  There are numerous examples in the Vue galleries here of terrain renders which are very realistic.  Take a look at some of Chipps stuff or Ken Was's posts.