Since I'm getting a master's degree in fine art I might as well put it to use and speak from my liberal intellectual high horse:
I would simply point out that most of the arguments used to define video games as "not art" are faulty and inconsistent with art history.
1. Interactiveness: some people think relinquishing agency/control to the audience disqualifies it as art, but there is interactive art in museums all the time and it's never questioned as art (because it's in a museum, duh).
Also, think about religious iconography of the Middle Ages, we cherish it as art, but it was never intended to be the personal expression of an individual artist, rather it was commissioned by churches and designed for the masses to sit around and pray in front of; and also to "educate" (indoctrinate), in this case to teach Christians their mythology, since most people were illiterate and the Bible wasn't widely available until the printing press was invented.
- interactiveness/audience participation does not disqualify something from being art.
The argument is faulty to begin with since while the video game player has some control, he/she is still bound by the internal world, its aesthetics, parameters, characters and storyline as predetermined by the creators of the game.
2. Video games as construction or programming rather than art: this flies in the face of art history as well, since many of the masterpieces were not made by one person. Michelangelo for example did not paint the entire Sistine Chapel ceiling himself, he had a team of dedicated workers who did most of the grunt painting for him. During his time, art was considered a trade skill, it was considered work, not inspiration.
Today, Dale Chihuly (I think he's still alive) creates beautiful glass sculptures, but he doesn't make them all himself, he has a team of glassblowers. He only gets more of the credit because our society loves celebrities, so he gets the press.
- Mechanical construction does not disqualify something from being art.
3. In fact, the whole idea that an "artist" is an individual genius is a modern, Eurocentric idea (and dare I say, a pretentious one). Other cultures and value systems have broader definitions. One of the professors I studied under, Henry Drewal (http://www.henrydrewal.com/) points out that in plenty of West African cultures, art is defined as "embellishment of form", they don't separate the aesthetics from the construction process or the work's utility, whether cultural or mechanical (i.e. whether it's a religious icon to be prayed over or an embellished column supporting a roof).
Drewal applies his awareness of non-Western cultures to contemporary Western popular culture and talks about "creative people" which includes not only the pretentious, famous individuals whose overpriced work gets stuck up in museums; but also the millions of talented, hard-working people working in fields like illustration, television, film and video games who are constantly contributing to the visual culture surrounding us, but who don't get the credit they deserve because of our culture's fetish with worshiping celebrities.
Actually I used Drewal's ideas in an essay defending video games as art.
- the image of the artist as a celebrity genius expressing himself is a narrow, Eurocentric (and probably upper class) idea.
Sorry if any of this was said already I didn't read all the posts. Basically this was the gist of the essay I wrote for grad school.