the buildings look really nice, but the "bryce" grass instead of the standard civ grass looks out of place.
What I did was render on a fairly flat free surface. Turn the sky "off" and set it to the same color (do you see the horizon in one of the images? It looks a bit off.). Turn haze and fog off.
export the image after render, cut out the flat green (but not the shadow) and paste the image (minus the grass, but including the shadow) on top of a civ3 style grass. Also, your selected ground cover is much too dark. It makes the entire image very dark, but it calls attention to the fact that your ground is nothing like the standard ground nor like the ground within the game.
Or, if you are more patient, render over a bryce grass. But again have the sky set to be very flat. Or place a giant plane with the ground texture to block the horizon.
Also, the angles of the buildings are different. Most building renders are done from more or less the standard Civ viewing angle. The camera set to around 4500 3500 -4500 if I remember correctly (don't take my word for this angle). There are often variations from artist to artist, but typically not so much within the same release from the same artist. I know I varied a little, but it was as I was learning how to do stuff. I know you already know how.
Also, the position of the sun in these images more less wipes out the shadows robbing the images of some of their vibrancy.