Its a tough call. The word 'art' has gone to redefine itself over the past centuries or so. Its funny that while Mr.Ebert said that games couldn't be art, yet his medium of choice, film is. It comes off as hypocritical in some ways.
No doubt that Ebert's antecedents regarded movies, 'moving pictures' as trite and a waste of time. I'm paraphrasing Movie Bob aka the Gameoverthinker( which discusses this issue on Screwattack), but they wouldn't consider movies art, since it was a collabrative effort, instead of an novelist, painter, sculptor, who takes sole credit for their creation. The movie auteurs then had to spin the defination that its the director's vision that brings the movie to life. Still, there are producers, actors, hair and make-up artist (which begs the question: Are they artists?), special effects people etc that make a film engaging. Art got redefined.
To take it a step further, Mr.Eberts detractors would probably tell him to read a book, check out the classics from medieval literature, to surrealist poems, that is if they were hip that bag on the latter. Those old crusts in turn, back in their youth, were probably told to put down that Dickens, Mark Twain, Cervantes, as they were considered at best, nonsensical, or worst, tools to subvert the youth. Get the picture?
It seems that through time, things that we know consider art, weren't always held in high regard in their time. The case with video and computer games, is that they've come a long way in such a relative amount of time. From the Odessy in '72, to the present, we went from proof of concept 'wow, we CAN interact with our televisions/monitors' to day a wide range of styles of ranging from mainstream blockbuster, to quirky off-beat titles. That'd be like if in film, they went from the silent films of the late 19th, early 20th century, to 3d, CGI films in the span of 1.5/ 2 generations. There's some growing pains to be had, and some reflecting to do.
The tl;dr version? Again, I share some of Gameoverthinker's sentiments that yes, games can be art and that for our generation the word 'art' got redefined, but it is good art? Not all the time...