There's a laudatory term that occasionally gets thrown around when we talk about videogames as an art form, but is not very clearly defined. What do we mean when we say a game is "deep"?
Depth in a game context is generally meant to signify the same thing it does when we talk about literature or film -- complex and thought-provoking, with layers of meaning that reveal themselves only when we invest the effort to discover them. In the interactive medium, this may mean that the story branches in interesting ways, or that we can choose to discover things about the game's world that aren't strictly necessary to finishing the game, but the discovery is rewarding in itself.
In this sense, contemporary open-world games with role-playing elements are generally considered to be deeper than the linear action games of old -- the player can choose which challenges to tackle, and in which order to tackle them. Some general constraints must exist to preserve the structure of the game's storyline -- an area may be off-limits early in the story, opening up after some significant event occurs -- but the player feels free to wander around, experiment and explore. As the form has matured, depth has also come into play in character development. We may make decisions while defining our character, if such options are offered. More significantly, how we interact with other characters, and with whom we choose to interact, may affect the story and our own role in the unfolding drama.
But this is not always the case -- some games don't have a story of any substance, and so complex, character-driven games make fine examples, but don't provide us with a solid working definition.
When we say a game is "deep," it can also, simply, mean that there are a number of interesting and worthwhile options available to the player. I spent some time with the Raiden Fighters arcade trilogy recently, and each game allows the player to choose a fighter from a lineup of aircraft with different handling and weaponry capabilities. For purposes of balance, this usually means that a slower craft has stronger weapons, and vice-versa; a fast, heavily-armed option would tend to make the other choices irrelevant. Good design attempts to ensure that each player finds an option that suits his or her style, without a burdensome disadvantage compared to other players.
Is my choice of which plane to fly against the incoming enemy forces a story point, or an intellectually interesting decision? No, but yes; it makes a difference to my experience of the game, and my preferences will likely differ from those of another person. Action really IS part of the meaning of video and computer games when we look at them as art; the choices we make become part of our own experience. Whatever art a game may offer is collaborative in nature -- the designer gives us a framework, and we explore that framework as we see fit. We may have fun in ways the designer never intended, or miss something the designer felt was important because our interest is drawn to something else.
So in terms of gaming, I suggest that "depth" really means choice: freedoms by design that allow each player to experience the game in a personalized, somewhat unique way.
This simple definition has complex ramifications. For example, it means there can be "false depth," an illusion of choice that doesn't really mean anything in gameplay terms. An example manifests in a common criticism of fighting games -- a broad array of available characters sometimes masks the fact that several of them are essentially the same. If there's no clear reason to pick one character as opposed to another, very similar one, these are not "choices" at all. Exaggeration makes us feel cheated.
I think this gets at something fundamental about games: interactive entertainment's true value, as art, has to be driven by interactivity. Looking at a game on a screen, watching someone else play it, is wholly insufficient. Game appreciation has to incorporate experience. And therefore depth has to exist at the gameplay level -- we have to develop a personal stake in what happens, a style of approaching it that reflects who we ourselves are, as much as the game's designers. Too much repetition or clumsy "game-iness" about the action reveals the illusion -- if we begin to feel like we're just pushing buttons at random, the fun vanishes.
Don't get me wrong -- music, graphics and storyline are important, and aesthetics can contribute energy and atmosphere that engages our minds and emotions beyond the game's mechanical objectives. But just as a good movie cannot be made from a bad script, regardless of budget, neither can a good game be built on poorly designed mechanics. Audiovisuals may dazzle long enough to get a few glowing reviews into print, but the truth will out over time.
So I would argue that Ric Ocasek was wrong. When we assess a game as art, it doesn't matter whether it was "deep." What matters is where we've been.