Until we develop some kind of quantum field recorder (A device that could be pointed at an environment or person and construct a working model of it's dynamics), the game actor's performance is usually split between the work of multiple artists, modelers, and voice actors. Each character in a AAA game is the result of a collaborative effort. 

Game actors in games that allow the user to have some autonomy over navigating their spatial environment, retrieve some qualities of stage acting - specifically that of the "total" performance, that can't be cut or edited.

Most modern game characters fail, because the techniques used to create their presence are based on film conventions and not stage conventions! The dialogue is structured like movie dialogue. Contemporary game developers must look deeper into the history of drama and stop watching the movies they grew up with!

Benjamin mentions the loss of a film actor's ability to react to an audience while performing.

Fortunately, game actors have regained this ability through system dynamics. Currently the algorithms and systems for dynamic acting are still being pioneered. The most latest notable efforts include Facade, and (very recently) Prom Week.