One obvious difference between art and games is that you can win a game. It has rules, points, objectives, and an outcome. Santiago might cite a immersive game without points or rules, but I would say then it ceases to be a game and becomes a representation of a story, a novel, a play, dance, a film. Those are things you cannot win; you can only experience them.Ebert tries to set up definitions in a way such that games and art are mutually exclusive. That is, that the difference between art and games in the interactivity, the ability to affect the art itself. I disagree. Much like a tree falling in the woods, can a piece of art that is not seen, or not heard, or not read, or not watched, be considered an art? Therefore, it is necessary to concede at least the minimal level of interaction, between that of the person and the art. Then, why does further interaction, that of the participant being able to effect the world presented by the game, remove a game's ability to be art?
Second, the point has been made that the participant's interaction with the game is not that of one who wants to interact with it as 'art'. Well, if I were to use any famous painting, say, the Mona Lisa, as toilet paper, does that make it not art? (Well, maybe after I've made use of it...)
To conclude, here are some games that I consider to be art.
There are the various art games that indie producers have made. Jason Rohrer has made many such games - in particular Passage and Gravitation. (I also saw Sleep is Death on the front page of HN a few days ago). No points, no rules, maybe an objective, so perhaps Ebert wouldn't consider those to be games. 'The Path' is another such art game, though again perhaps Ebert might not consider it to be a game.
There are various RPGs that are particularly story intensive. In fact, a common complaint seems to be that there's too much cinematics and story and not enough gameplay.
Finally, I consider the game 'Prince of Persia: The Sands of Time' to be art. Maybe not its sequels though.