The example image you posted has a greater impact because (1) her eyes are looking directly at you, creating an intimacy and (2) the camera is zoomed right in to the figure, enhancing the intimacy even further. In your picture, the viewer is simply looking at a scene. In the other image, the viewer feels like they're part of the scene.

As Jenx says, lighting is important. Composition, though, is arguably even more important. The camera angle and point of view should engage the viewer.

Posing of figures is critical too - care taken with posing can add an air of believability to a scene which even great lighting, GC, realistic shaders etc. cannot do by themselves.

Check out the Nikki Sprite comic at
[link removed]

Go back to the first page of the comic and read it all the way through. That's how to do it.