To me art is something that can evoke emotion to the audience. Many have pointed out the story and visual presentations, and I believe that's certainly valid, but I also think game design in itself can be considered art.

In more words than I care to write, Vivi22 has pretty much explained this. The process of designing something to create an emotional rollercoaster for the audience, to me, is a good sign of what is art.

Case in point, outside of Vivi22's examples. From what I've seen at E3 and what the developers are talking about, this is pure art even moreso from a game design point of view.