I had copied in a definition of the word "Art" into my post but ended up deleting it because I didn't agree with it. Said definition stated that it is only art when the reason it was primarily produced was for it's beauty to be appreciated, which isn't the case for any video game. They're all made to sell and to entertain. Artistic merit is a secondary concern. This is the same with most modern mediums such as movies or literature. It would be kind of irrational to preclude things from being art just because it's primary concern isn't to be appreciated.
However, if we think of art as the product of human creativity in the form of something profound or beautiful, something that truly has an emotional impact on us, then I think we have a much better definition. In this sense all games can be defined as art, because the beauty of anything is subjective. I realise I'm rambling here but if beauty is subjective, and art is something beautiful made by human creation, is what can be considered art subjective as well?
Anyway, now that I've got that out of the way, the only game in my collection which I, in my subjective opinion, would say is Art is bioshock. I liked it, it was deep for a game, it had something to say about individualism and some of the plot points and characters were simply fascinating(particularly the part about Steiner).