I think there's a reason two of our most beloved games--chess and poker--are also major contributors to our language. Expressions such as "checkmate," "pawn," "playing the hand your dealt," "calling his bluff," "ace in the hole," don't have real linguistic equivalents. They are areas of expression these games have claimed a monopoly over, and it won't take much effort to find many other expressions that find their roots in games. It's not mere postulation that games could be used as expression--they already have been!
What is art? I know you've heard the question a million times, but you haven't heard my answer yet. You see, I'm utilitarian at heart. I think in terms of utility. Therefore, if A gives me the same utility as B, A and B are equivalent. I get calories from pizza, I get calories from hamburgers. While they are different in many significant ways, they find themselves identical when both are abstracted to "food." I see no reason not to view art in similar terms.
I use "expression" and "art" synonymously for the most part, mostly because I don't care for the baggage of "art" and I'm aware of the ambiguity of "expression." The two concepts are slightly different, however, though closely related. "Art" is an expression that uses an artistic form. You can say art is a "formal expression," in that it uses a defined form to promote the expression.
But what is expression? Expression is related to communication, the transmission of information. Humans generally concentrate on transmitting information via denotative language. Denotative language suggests that one idea may be used as a representation of another idea. The sound "blug" is an arbitrary vocalization, but if I can tie that sound (one idea) to a particular object class (another idea), I have created a way to refer to the object class without having to point at it all the time--which will come in handy in cases in which the object class consists of man-hungry animals with sharp teeth and nasty dispositions.
However, there are peculiar ideas that are unable to be shared in this fashion. These ideas are ones essentially one's I can't "point at" in order to reference. They exist solely in our minds, and as no one can look into anyone else's mind, it would seem like we are doomed to leave these ideas un-transmitted.
The solution to this problem is the creation of a sort of proxy language, which is called connotative language. This language also uses objects in the "outside world," but not as representations of ideas. Instead, it arranges objects in a way that aims to induce the idea itself in another's mind. This inducement of ideas themselves instead of representations of ideas is "expression."
Going back to my utilitarianism, if I were able to induce an idea itself in you by using an expression in a particular form, wouldn't that be art? If I used music, of course you would say, "Yes." If I used sculpture or literature, you'd again say, "Yes." But would you hesitate if I expressed that idea to you through the rules of a game?
The expression of ideas that lie outside the realm of denotative language has long been a noble goal of humankind. It is an enterprise that has everything stacked against it, and yet there is a tremendous will to defeat the odds and connect on the deepest levels imaginable with family, friends, and neighbors. I see no point in turning our noses up at potential tools, at handicapping ourselves out of decency's sake. You don't get points for being "proper" in this endeavor, you only miss out on the chance to strengthen the bonds that unite us.
There was a time before they hung paintings in museums, before they taught music in schools. How did the people back then recognize art? Did they take a vote at town hall? Did they wait for their kings to proclaim it so? Or did they look at a painting or listen to some music and say to themselves, "Through its artifice shines the natural, through its ineffability rings the truth, through its design I see infinity, and in its creator I see myself"?
In the end, isn't that good enough?