I haven't played
a lot of open-source games so I am by no means an experienced open-source guru in that department.
However, comparing the open-source games that I have played to closed-source games, in general, it seems that they are not as good. It seems that their direction is not quite as refined or organized enough. Now, one might say, Of course closed-source games are better, the developers earn a salary, but even those Indie, closed-source developers who don't get paid still seem to make better games.
On another front, other open-source software such as Linux seem to compete just as well or better (quality speaking) with their commercially made competition.
I believe that creating games is an art, not a science - it's goals are for subjective results.
The goal for Windows and Linux may be the same: Create a great operating system that works well getting jobs done. It wasn't designed to invoke an emotional response from your audience, it's just there to get things done the right way.
Video Games, on the other hand, are for leisure activity just like watching a good movie. Imagine watching an open-source film, where anybody could be an actor, write a piece of the story, or design part of the set. What you would have would be a mess (something like Monty Python and the Holy Grail). Perhaps this is not the best analogy since open-source games pass peer-review before going into the final product. This is not to say that it is a fail-safe process, however, as a lot of things do slip through the cracks especially when the game has been in development for many years and very few eyes are watching.
I think Independent (closed-source) game developers are popping up more and more lately, and their quality is getting better and better. In the future I see closed source, indie games becoming more and more popular, rivaling the commercially-made stuff. At least, I hope this is so, because it seems that the greatest innovations to gaming come from the closed-source independent developers.