All these games have all these fancy features, but I think Doom III will do the best job of integrating them into every aspect of the game. For example, John Carmack said in an interview that if a feature is used, it should be used consistantly throughout the entire enviroment. For example, in Doom III, every surface has a bump map. As for the screenshots looking like plastic, I think someone once said that the reason for that was the gamma was cranked up way too high. In addition, the game looks exponentially better in motion, especially when you take into account the dynamic lights acting on the (universally used) bump maps.
No doubt that Half Life 2 will be good as well, but the two games are not very comparable.
------------------
I check my e-mail.