Over the years, the realism of Google Earth has improved quite a lot and there are things you can do to make it more realistic.
The first one is pretty easy; simply by enabling the 3D buildings (powered by the auto-generated 3D imagery), you’re off to a great start. While the 3D imagery can look pretty bad from low altitudes, it looks stunning when flying over a city.
The big key to making Google Earth look awesome is to enable the photorealistic atmosphere, along with the “sun” and “water surface” features. By doing the above, you can end up with a scene similar to this:
These features can be quite resource intensive for your computer, so most people can’t leave them enabled all of the time, but they can have an amazing impact on the realism of Google Earth.
If you’d like to take it a bit further, this article on anti-aliasing and anisotropic filtering will help you understand some of those features a little more as well.