I can understand Heavenly Sword not being there because it was produced in Japan. The intent of these awards seems to be to try to legitimize writers so the WGA can get them unionized.
This is NOT the place to discuss whether that should happen, but I'm reasonably sure that they deliberately picked games with a small group of writers that were produced in America.
For instance, BioWare is Canadian, and the writing for The Witcher was assumedly done at Atari (the publisher)'s studios.
Dammit, World in Conflict was made in Sweden, though.

It was published by Sierra, though, so... maybe the translation was written here?
Jam it back in, in the dark.