It's worth taking a few minutes to watch this art-design trailer for Team Fortress 2. It references influences such as the phenomenon of increased recognition through caricatured silhouettes, as pioneered by early 20th century commercial illustration, and the background plates from Hayao Miyazaki animations. It gets a bit technical towards them end, but it gives you some idea about the layers of technology that are being artistically smoothed on to games like this. In videogames like TF2 art and science really do meet to give us the best of both worlds.
Team Fortress 2, like World Of Warcraft, isn't going to age particularly quickly. Unlike games that reach for realistic visuals, these more abstract, stylised graphical themes do not lose much to the ongoing race for visual fidelity. The understand their visual systems, and are just fine with them, thankyouverymuch. Perhaps TF2 could even be a turning point for art design in PC gaming - proving that the tech developed in the last few years does not have to be put to use creating increasingly realistic people and worlds - because what really matters is character, personality, and easily comprehensible environments, and not a really life-like space-soldier.