Unfortunately, Yahtzee ninja'd me and said exactly what I wanted to say about the whole "Roger Ebert says games aren't art" thing. If you want to know my take on it, just read his. I tried just crossing out his name and turning that in as my weekly column, but Susan caught me and made me write "I will not plagiarize Yahtzee" 500 times. (Thank goodness for copy / paste.)
For the lazy, my position is that I disagree with Ebert. (Duh.) I think games are art, but I think Ebert is a great guy and not quite deserving of the hate and vitriol gamers have been hurling at him. He's a guy with an opinion. Like all critics, he is valued not because his opinion is somehow more valid than anyone else's, but because of the skill and depth of knowledge used to share that opinion. Honestly, if I had ten minutes with the guy I'd much rather spend them talking about movies than browbeating him because he refuses to take my hobby seriously.
So instead of just re-hashing Extra Punctuation, let me cheap out on you and talk about games that do the "games as art" thing really well.
If you had someone who wasn't a serious gamer and who was undecided on the issue of "games as art", what games would you have them play? It's a more difficult question than it seems. Remember that you're trying to persuade a relative newbie. It's no good throwing them into a shooter where they will have to learn how to play before they can make any progress. There's not much art to be found in the game over screen, and they will most likely be frustrated long before they're engaged. I'd also steer clear of games that already have tons of media saturation. My goal would be to show them the area of gaming they haven't seen. I'd also avoid really bloody games. Show someone God of War and then later ask them what they thought of it. I'm willing to bet they won't comment on the story, mythology, architecture, music, or character designes. Instead, they will remember the flying entrails and severed heads. I'd also stay away from long games. I don't think the skeptic is going to be willing to play ten hours of Final Fantasy before they can get to the part where the plot takes off. Lore-heavy sequels like Metal Gear 4 are also a bad pick. As a newcomer to the series, I can promise you the story and setting of MGS4 are incomprehensible gibberish if you don't have someone sitting beside you and explaining who these people are. (My brother is a huge Metal Gear fan, and even with his help I was still baffled by much of what was said.)