Warning to the TL;DR crowd: Wall-of-text ahead.
I've had and expressed thoughts on this very subject both here on the Escapist forums and elsewhere. Only thing I can say to Roger Ebert is, you are a well respected and prominently successful film critic; however, in my opinion, you may need to expand your perspective.
In my opinion, games are an artistic medium and, therefore, have the potential to be made as art. The unfortunate problem is that only a few games have ever successfully achieved the status of being art or artistic(Yahtzee mentions Shadow of the Colossus; Ico is a personal favorite of mine as an example of the artistic game because of its consistent style, interaction, story, and the emotional connection with the main characters, being the only game in which I actually cared about the protagonists). I attribute this primarily to the source of the game, i.e. the game developer and game publisher. Basically, game developers are cut from the same mold of geekery that many of us are and, thus, usually lack in artistic sensibilities or an understanding of what makes something artistic. Game publishers, being more motivated by pure profit, seek quick sell short-cuts to boost their revenue, hence the high reliance on the more basal aspects of sex and violence in games and a glut of sequels and clones on the market(this is what sells, and this is what gamers are buying, plain and simple).
To me, art is not created by any one singular element in a work, and a detailed, pretty picture is not necessarily art or artistic(any trained monkey can learn how to make a detailed, pretty picture). Art occurs when different expressive elements are juxtaposed and made to cooperatively interact in such a manner to create a coherent expression of an idea, concept, thought, emotion, or perspective. (This is why, in my opinion, a game that has a bunch of cool elements slap together is not artistic; it's just a mess. Art requires its elements to work together to create a cohesive whole. Coolness, unfortunately for art, is the ultimate expression of individuality and uniqueness and does not seek to cooperate with anything; it tries too hard to stand out on its own and competes with the rest of the work for the observer's attention.) Art often forces us to examine the "human condition" and the "human experience." Art also can allow us to explore alternate possibilities of reality and perspective and test how the human consciousness would react and interact with such a reality. Art makes us feel, question, and explore our existence.
In my opinion, most video games don't really take this particular spirit of artistry. Instead, most games seem to be based around trite, mindless violence and a juvenile attitude and perspective of sexuality and adulthood. They're just base, hence, failing to be artistic. Often, game developers try to use extreme detailing of visual imagery as a means of achieving art; however, such efforts often fail to create art for the reason stated above, that detailed, pretty pictures are not necessarily art or artistic.
In my opinion, for games to shift more toward being artistic, gamers have to become more discerning in their taste of games and be willing to support the more artistic games by purchasing them. At the same time, the talent pool of game developers has to become more knowledgeable of art and what makes art(take some art appreciation courses, maybe), as well as learning how to create art as a concept rather than mere repetition of mechanical technique(this is the trained monkey creating the detailed, pretty picture). It would also help if game developers expanded their own repertoire of ideas and experiences, rather than recirculating the same old stale ideas that we've seen time and again. Also, game publishers need to be more willing to invest in innovation and experimentation of new ideas rather than forcing output of the same old junk(how many Guitar Heroes, Haloes, Metal Gear Solids, GTAs, God of Wars, and Devil May Cries do we need?). Finally, the gaming press needs to give more space and journalism to the lesser known but more inventive game titles, rather than fill their publications with a glut of the same games(and the same information about those games) about which we've known and have been hearing for months on end. Basically, give new, fresh ideas a chance to percolate to the forefront. Sure, not all will be great hits, but you never know when you may find that shining jewel amongst the steaming pile.