Thanks to this reddit thread, here's a look at Skyrim's face tech compared to Oblivion's and Morrowind's. The improvements are noticeably drastic when shown in comparison, especially the improvement in wrinkle-modeling technology. I mean, look at that Imperial's forehead. It's so rugged in comparison to Oblivion's weak, smooth foreheads.

The full image can be found here. I think my favorite difference is between Oblivion's Argonian and Skyrim's Argonian; Skyrim's design makes them look much more lizard-like, rather than Oblivion's design which makes them look a little too ridiculous for my tastes.