Here is the website. So now even video games count as "an artistic medium," eh? It really makes you long for the good old days when we were debating whether or not "art" included a picture of some fag with a bullwhip stuck up his butt.
What makes art art? Well that's an empirical question, not an a priori one. We just look at everything that people treat as art -- all over the world, and back to the beginning of our species history -- and try to see what traits they all have in common. Otherwise it's pointless exercises in arguing over what words mean.
There is great disagreement over this empirical question, mostly stemming from how common is "common" across cultures, and how "timeless" is timeless. Still, here are two traits that never make the list of "what makes art art," and that if you were to include them, everyone at every time would say, "God no, that would make it not art!" Both relate to how much control the audience has over the experience.
1) The audience chooses the outcomes for at least one, maybe all, of the major branching points in the experience. E.g., what should happen to a character in a narrative, whether the next movement in a piece of music should be frenetic or calm, etc.
2) The audience is required to participate physically to advance the experience along. E.g., having to jog in place to move the first act of a play along, then switching to squat-thrust in place to move the play into the second act, or having to trace certain patterns with your finger over a page in order to move a print narrative along. Turning a page is not participation, and neither is keeping your eyeballs open, getting a source of light to see the page, etc.
Of course, both of these are essential to video games, so video games are not art -- no more than a crossword puzzle, a Mad Libs story, or a jigsaw puzzle (the puzzle and the final picture formed are not the same thing)
Academic morons aside, everyone everywhere believes that the artist and audience are distinct, however much they may or may not interact when they're face-to-face. So a work of art must be created by the creators (sounds obvious, but again those are the times we're living in). If a so-called artist kept asking us to make this and that decision about where the experience should go, we would conclude that he couldn't make up his mind and had given us a very incomplete work of art. Make every decision for us, and then it might be art.
As for physical participation that must be of a certain form at certain times along the experience, that puts the audience in control rather than the artist. We in the audience want to be taken on a journey, led by the expert storyteller, singer, movie-maker, or whoever they are. We might have a physical reaction to this guide-tour through their imagination -- dancing along to music, stabbing the air with our finger when some character gets what's coming to them, and so on. But our actions are never required to move it along.
What popular, mass-market things would qualify as art, at least on these two requirements? Just to name some examples that are close to video games, and leaving aside obvious things like movies and TV shows, there are comic books, pro wrestling matches, and the dark rides at amusement parks. They offer narrative content and visual spectacle, like video games, but the distinction between creators and spectators is maintained. Based on the relative lack of interest in these art forms compared to movies, TV, books, etc., it doesn't look like comics, wrestling, and ghost train rides are the best vehicle for artistic creation. But they at least make the cut, while video games do not.