Hi
I have to decide if Unity is suitable for a new project. I have watched some demos.
What strikes me is that in a lot of the demos the pictures seems like being drawn by a pencil. This looks very artificial to me.
Is this a choice of the artist? Or is a typical effect of using Unity?
I think you need need to look at Unity showcase.
it’s the artists choice… If you buy pro you will have even more artistic choice 
Don’t go free Go Pro!!
What it create that effect, is the lack of lights so the whole textures are flat. Even if you don’t want to use dynamic lights, embedding some static shadows in the texture can avoid that effect. For tiled textures you can use lightmaps.