Yeah it's obviously photoshopped - skin is smoothed out, teeth probably whitened, eyes and reflections tweaked etc. - but nevertheless, the facial wrinkles are still quite visible, even the tiny ones around the eyes.
These are actually pretty damn important, as our vision system (including how the brain interprets images) is highly tuned to notice these features, in order to interpret the emotional state of the human in front of us, which is an evolutionary advantage. You can actually tell that the retouching was done by a highly skilled artist, because these wrinkles are completely preserved, despite the almost complete loss of all other skin detail. Less skilled DTP operators and software solutions would probably smooth out these as well, leading to a less pleasing / more disturbing result.
Funnily enough, facial expression wrinkles are something that most celebrities (especially women) hate with a passion. The reason is that the resulting wear weakens the skin tissue and the wrinkle lines will eventually become permanent, even when the face is in a neutral expression.
If anyone has watched Coupling (a great British show), there's this sort of running gag about Sally. She states that now that she's turned 30, there's only a limited number of smiles left to her before her facial skin becomes all wrinkly and old; so from now on, she's only going to smile at handsome men
This is also the reason behind using Botox and face lift plastic surgery, the aim is to try to preserve the appearance of youthful skin that hasn't yet been stressed hard. But none of these work particularly well IMHO, you can almost always tell that something's wrong; and that's also why these people look weird and appalling.
Also, I strongly believe that there has to be a genetic element in this. See, I'm 37 and yet there are almost no lines on my face, expect the 'smile' wrinkles at the nasolabial fold; whereas I've worked with a guy who's still only 29 and yet there are some pretty deep lines on his forehead
Going back to CG characters, I think the conclusion should be pretty straight now - the lack of such strong wrinkles while making various facial expressions will inevitably feel weird, just like looking at people who did Botox or plastic surgery. It also makes it harder for our brain to interpret the facial expressions and thus the underlying emotional states, making us feel alienated from the character, ruining even a generally super realistic face.
And I also have to note that I suspect the lack of these features on UD's certain faces are not a result of the art team's lack of understanding, and have more to do with the talent's unreasonable demands...
