Again, though, if you look at art history, one of the criteria for calling something "art" is usually- but not universally- that it was created with the intent of being art. It is a conscious and deliberate act. IOW, there is a distinction between when Jackson Pollack merely threw paint at a canvas- say, because he was bored or upset- and when he threw paint at a canvas to create Ocean Grayness. There is a difference between when Joe Satriani noodles around or practices his scales and progressions, and when he actually sits down to compose.
To further burwongle this up, something's status as art may change from Not Art to Art depending upon presentation. If Satriani's producer has the tape running, and then uses Joe's noodlings as the sample in a rap tune of his own, then those noodlings become art...as well as possible copyright infringement, violation of fiduciary duties, and so forth. (See also Duchamp's Urinal.)
Sturgeons' Law aside, 99.9999% of the time when you sit down to play an RPG, you and your cronies are not consciously setting out to create a work of art. It may be aesthetic in some way, but without that intent, it falls short.