His article is elegant in it's defense of his personal feelings, and we run up against the age old question: Is it Art?
Here is the rub. Gamers (of which I am not) view their games as art, as storytelling, as an immersive environment that fills their senses. Mr. Ebert, who comes across a lot like a grumpy grandpa who knows exactly what he is talking about, despite having never tried it (sorry Roger - I have to call that one the way I see it) comes at it from an equally valid point of view, that of knowing what you like, and appreciating it.
Ever since man rubbed charcoal on a cave wall there have been people who want to tell other people what is art and what is not. There are roughly 7 billion forms of self expression on the planet, each of them represented by an individual who has their own way of viewing the world, of expressing themselves, and of appreciating art. They are all right.
The gamers are right. If they view their games as art, then they are art. They are as much art as The Meat Dress, as David, or as Rothko. Just because we don't understand or appreciate the message, structure, sentiment, or even form of something does not mean it's not art to someone else.
Art, like beauty, is in the eye of the beholder. Trying to tell someone who feels that The Meat Dress is not art all the reasons why it is, is simply an exercise in futility. If they don't see it as art, then it is not art to them.
For gamers who see their games as evolving art, it is art. For Mr. Ebert, it is not. There is no fight, it's simply a matter of how people see and feel things differently. I see a world of possibilities for art in the dust blowing across my sidewalk today... my husband sees another mess to clean up. It's all about personal vision.