Great graphics alone don't tend to make me think "art" when I play a game. The fact a game has great artwork doesn't make me feel like calling a game a piece of art. Game has to strike some kind of emotional chord. I haven't played Journey, but even just watching the videos, that game stirs something in me for some reason, even with no dialogue/typical action.
....for me personally, I think the music score (and to lesser degree, the sound effects) in a game has the most effect. I could play Stronghold or Majesty all day because of the music. Games with older style top-down graphics (which were nice for the time, actually)...nothing like all the fancy "realistic" 3D of today...but because of the music, I felt emotion during battles, feel oddly attached to my duplicated units and peasants, blah blah. If I listen to those scores, I relive game moments. Or something.