Yes, there are two separate aspects to computer games; the software engine,
and the artwork, including graphics, audio, cut scene video etc. I think it's
essential for the software engines to be free code, for all the reasons
others have mentioned here relating to user rights and protections. As a
CreativeCommons advocate, I prefer games that at least allow free
distribution, and I love the idea of games that license their art under a
license that matches the spirit of their software license (GPL/ CC-BY-SA, or
Apache 2.0/ CC-BY). I definitely support the development of libre games, and
projects like the Liberated Pixel Cup:
https://www.coactivate.org/projects/disintermedia/libre-game-development
But I also think that *right now* convincing companies to free their code (or
use free code developed by others or both, and maybe used a CC license with a
Non-Commercial for the artwork, is more realistic than convincing game
companies to release their games as free culture, for two reasons. One,
because as others have mentioned in this thread, ARR (All Rights Reserved)
artwork can't compromise the user's computer in the way proprietary software
can, and two, because at least for now, it's an easier case to make from the
point of view of the companies' interests.
The full explanation is long, but if you can be bothered bashing your eyes
against a wall of text I've put it up as a blog post on Disintermedia:
https://www.coactivate.org/projects/disintermedia/blog/2017/03/31/convincing-serious-game-studios-to-free-their-code/
