First, you need to define art, and the definition changes from person to person.
For me, art is something created with the purpose of being regarded as art. This is very important: if you do not intend your creation to be art, then it cannot be art. Also, this piece must also be meant to provoke or amplify some emotion or feeling in the viewer. This emotion can be fear, interest, curiosity, laughter, sorrow, even just awe at the technical skill of the artist.
Technique doesn't make art, though! Technique is what allows the artist to project the image in his mind into canvas (I'm using "canvas" as a big blanket word to mean anything that allows you to view your art: a CD with your music, an actual canvas, a reel with your film, a piece of paper, a wall, even Office Word).
With that said, I think most games (99,9%) are not art. Some may be artistic or artsy (Okami, Prince of Persia) but aren't really art because the focus is on the gameplay, which is essentially computer code, and programming isn't an art. What you create with programming, however, can be.
Here are some examples of games that I consider to be art. Notice the similarities between them: Ico, Shadow of the Colossus, The Longest Journey and Dreamfall. Ico makes you marvel at the art style, SotC made me drop my jaw in awe at the size and beauty of the Colossi. The Longest Journey was the gaming equivalent of a book you can't put down, and Dreamfall practically broke my heart during a certain part that was entirely optional, easy to miss, but the game had obviously been built up to reach that part.
EDIT: Another example is Today I Die. The ending brought a huge grin to my face, and the soundtrack fitted everything perfectly. That game is truly interactive art. Poetry in motion.