I think that some games are art and some are definately not. As an artist myself, I think that the intention behind art is encourage some kind of thought and emotion in the audience. Contrary to what has been said, the audience is actually very involved in the process of encouraging thought and prying emotion from a peice.
In theatre for example (my chosen medium) the job of the performers is to tell a story, and it's the audiences job to interpret that story as they see fit. A strong performance is one that evokes a powerful emotional reaction and makes the audience seriously consider the material. With games, the job of the audience is even more profound because the player is one driving the action, and more than ever is the audience free to react to the material in their own way. Besides, if the goal in art is to invite some powerful emotional response, then why are games that do just that not considered art?
Of course some games are most definately not art because the goal is solely to entertain and invites absolutely not emotion whatsoever. (Ex. MAG, Mario Kart, most Marios in general, Pokemon, Rock Band/Guitar Hero, and many, many others)
So overall, I don't think games NEED to be art per se, but some games with compelling stories and relatable characters most certainly are. Of course, anyone who insists that games HAVE to be artistic is just an ass, the number one goal of most games is primarily to entertain, and by most people's logic the measure of a good game is whether or not it's entertaining. Art and emotion and all that noise is just a bonus.