Comparison mostly. HD and 3D isn’t impressing you by virtue of it being superior to real life (it isn’t after all), it’s impressing you compared to other examples of the same thing done “worse”. The best portrait artist in the world can not make something look more “real” than the reference material, but it can compared to other attempts at painting.
This is true in other natural things as well. For example, a really big tree surrounded by smaller similar sized trees feels “really impressive” compared to a mountain surrounded by other… similar sized mountains. Or why a particularly colorful plant seems impressive surrounded by a bunch of green and brown plants.
On the other hand, things like OLED screens can be impressive compared to the natural world due to their ability to arrange and display colors rarely found in nature.