In an old thread Steempipe released a demo demonstrating a terrain mesh moving extremely realistically(with a shader)! Perhaps he'll release the code for that one day, i'd really like to try it out.
Your right about Half-Life 2 it didnt have any shaders that were intresting other than the water. Doom3 and Theif 3 were technical achievments in the terms of shaders but I stopped playing both of them after a few hours since the art direction and gameplay became boring. If only they mixed a little more than a grey/brown pallete of colors in with those shaders. My opinion btw - many people I know really enjoyed those 2 games art styles.