After some chewing-over of the subject with a friend, I've concluded a lot of this is about semantics. What video game lovers want, more than anything else, is for games to be respected. Calling a video game a work of art is just another way of saying that it's worthy of cultural esteem, and not just a frivolity.
This is something that can only come on its own. It's difficult to demand that sort of thing; the game, or whatever it is, has to earn it on its own terms. And I think some of that has already arrived. Video games have more respect as a cultural force now than they did ten or twenty years ago. There's departments in universities that study them; they're a force to be reckoned with in the world of IT; they stimulate the development of works in other media (movies, comics, etc.) and so on.
What you are not going to see, and what I think is misguided to long for anyway, is video games displacing other cultural commodities. Games aren't going to eclipse books or movies because, well, a book is a book, a movie is a movie, and a video game is a video game. People go to each of them in turn to get things they can't from the other, and to feel that one of them can only ascend at the expense of the other(s) is chicanery.
I hear how game lovers feel dismayed that the things they love are "not taken seriously", but that invites other questions: not taken seriously by whom? And what would such gravitas consist of? Bigger sales? Writeups in the New York Times? A dedicated category in the Pulitzers? It's hard to say they're not taken seriously, when there's that much of a space in the public cultural consciousness devoted to them, whether you're talking about Grand Theft Auto, Final Fantasy n, or Wii Fit.
So is Ebert right? I think he's right in that games are their own animal, that there's no crime in loving a game because it's a game, and that seeking approval from people who aren't interested in games on their own terms isn't worth the trouble. That we cannot get some people to think of games as works of art does not mean we must also therefore think that much less of them as games. This whole business of whether or not a game is a work of art is like comparing an opera to a drive in the country.