[SKYNET]

Try and work on your lighting and defining the focal more.
On the first, my eyes are drawn straight to the light colored C4Ds. The soldier seems a bit too dark.
On the second, you kinda have two focals, with that bright part on the right. The light would be better coming down from just behind him. Look out for the natural highlights, on stocks and renders. This will help to tell you where to put your lighting.
The third, the monster blends in a bit too well with the background.

Hope this helps, keep it up.