It depends on your definition of the word. Some say that video games aren't art because art is a creative expression, and expression is non-interactive. Others say that video games are art because they communicate ideas. For me it basically boils down to the intentions of the people who developed a given game. Like Eq said, if a game is supposed to simulate reality, I don't consider that art. But if a game immerses you in a different reality, then that's artistic, if not exactly art. A graphical style, a meaningful storyline with interesting characters, a soundtrack, a gameplay mechanic... most of these things are considered art forms, and when put together, they can create a very immersive experience. It's potentially much more powerful than a book, movie, painting, or anything else, because it can make you feel like you're directly involved. It's not strictly expression, but it can be a very effective way to communicate a set of ideas, which is the purpose of expression.