In a very non-technical answer. When I look at things, there is blur, and a lot of distracting light effect, and I doubt this can be replicated on a monitor. I find first person games really, really, fake. No matter how you see it, the main character is frequently seeing like a frog (massive peripherals), an eagle (telescopic vision), a fly (bullet-time), or a combination. The only time the character blinks is at the same time you blink.

That might be unrelated to the plastic look. But I think it's not so unrelated, people want to look like they have amazing supermodel skin, really shiny skin that's been rubbed with oil.

In a technical answer, all I know is it's the lighting. Movies can be tweaked by after-effects, and I stumbled over a WALL-E article about the movie makers spending half their production time to replicate real cameras. That means to make it look real a game developer may need to spend twice as much to finish the movies, and clean up plasticness.

Idk enough to say if this helps in real-time rendering, but I know there's plenty of baked rendering.

This almost but disturbingly not realistic look was one reason I stopped gaming. The other was the aforementioned shiny-dark design, like American rap videoclips have. CoD2 was "realistic enough" for me.

what wideoclips? (asking for curiosity)

pffff, I can't say anything specific. I was thinking about the pimped car in the night kind.