As you may know, I'm a devoted supporter of the Free Software ideology. Practically the only piece of proprietary software I (grudgingly) use on a regular basis is the Flash plugin for my web browser. Except... I'm also a gamer. And obviously the vast majority of games are not Free Software, on the console front practically none.
However, although games obviously are software, their function, role, market etc. differ greatly from utility software. It is easier to compare the game industry to, for example, the film industry. For regular software the community based development approach of Free Software simply works better than a conventional capitalist approach. However, for games that can really make the most of the technology available today you really need a team of professionals working full time, something that is only possible in a commercial environment. Also, a game is only part software. It's just as much story writing, audiovisual arts etc. Commercial distribution of games is really the only practical option.
OK, none of this of course means that the software portion of a game couldn't be produced using Free Software standards. In fact, I think the whole game industry would likely benefit from it. But I'm afraid that, whereas a Free Software computer system is already a perfectly viable option, changing the entire game industry would currently be next to impossible. It's not like you can choose a Free alternative to your favourite game.
But of course Free Software games do exist, both games that are entirely Free and games with Free Software components coupled with proprietary content. id Software has famously released the source code of many of their games (allowing them, among other things, to be ported to GNU/Linux systems).
I was going to write about examples of entirely Free games I've encountered, but this post is getting pretty long as is, and it's getting pretty late, so I guess I'll leave that for another day. Good night.