I looked back and realized I haven't defined "pattern" as I am using it. Durrrrr.
At first glace, a pattern is something, anything at all. However, the pattern is not the thing, the pattern is the doohickey that guides the thing's existence in whatever "gamespace" it occupies.
For example: a person exists in several kinds of gamespace. A person exists in "space", and in that their pattern would be defined as their graphical representation and its location/orientation. A person also exists in "time", and the pattern representing that is all that guides their actions. Of course, there are several different "time" gamespaces, since each time a gamespace interacts with another gamespace, it forms a gamespace. For example, the sort of dynamic "space-time" of, say, moving about and attacking. Or the longer-view "social-time" of the interpersonal interactions of the plot.
You can view patterns in any kind of gamespace, and you can have a lot of weird fun doing it. For example, what about viewing a character's pattern in "space-time-social" gamespace, which revolves around how the player moves through space based on their social interactions (and how those interactions change due to it). You can zoom in and out: are we talking about what the character does during this particular dinner party, or how their fifty-year-long marriage goes?
Of course, everything has a pattern in all gamespaces they exist in. For example, a rock has patterns. A machine has patterns. A nation has patterns. Genetic lines have patterns. A friendship has patterns. In fact, a particular gamespace is a pattern, built of all patterns in that gamespace. In double fact, a game is a pattern built out of the patterns of all its gamespaces.
And players love to figure patterns out. They're good at it, too: they have a long list of patterns they already know and they tend to base their predictions on.
The key is that we create the gamespaces the patterns exist in, so we can mold the patterns to be any kind of experience we want. Usually, our games revolve around space-time gamespace, with some social-related linear plot gamespace. That's fine: you simply have to understand what you're doing.
What you're doing is creating a pattern that the player will explore.
The problem is that players have different preferences and capabilities. Everyone's ability to comprehend a pattern is based largely on the patterns they have already collected over the course of their life. Generally, the more of a particular breed of pattern they've seen, the more likely they are to enjoy seeing a new model... but the more discerning they will be regarding flaws and unlikelyhoods.
With static patterns - like a linear plot - this importance is largely mitigated. The pattern doesn't require expertise, because the player can't change it. It doesn't require a robust model, because the player will never see the model. A player might be confused or bored with the pattern, but he won't suffer unduly due to it.
But with interactive patterns - like gameplay - this is critically important. My mother could never play Baldur's Gate. The pattern is absurdly complex. On the other hand, gamers didn't much like Daikatana - the pattern was too simple and transparent. In addition to requiring the player to have a certain level of skill, these patterns are also explored on a whole new level, exposing the guts of their operation to the player. Whereas a shoddy plot line might skim by okay, a shoddy gameplay algorithm will result in an experience which is repeatedly broken by hammering on the crappy simulation point. Dominant strategies are your enemy in almost all situations: a "magic bullet" move renders every other part of the pattern wholly irrelevant. Who cares what the deep inner secret of the bad guy is, when the bad guy takes three seconds to kill and can't hurt you?
I'll talk more about that when I get into pattern depth, but here's an interesting corroboration:
Movies follow the same kind of system, even if they don't do it on purpose. You'll notice that there is a relationship between how much a pattern interacts with your window (usually the main character) and how detailed the pattern is. Obviously: the more you look at a pattern, the more detailed it gets. But it's more than that: a pattern's value is measured in relationship to your window. In a game, that's almost always your avatar. In a movie, it's usually the main character. If a pattern doesn't affect them, most people won't care.
Interaction is the key to making patterns interesting to the audience. In a linear story, interaction is carefully predefined. In a game, interaction is loose and free.
Are a hundred non-optimal interactions worth as much as one optimal interaction?
Yes, because those are a hundred non-optimal interactions are truly interactive, allowing the player to more fully explore the pattern. And, as we'll see in my pattern depth post, nothing is more important than exploring a pattern.
Even if the pattern is flawed, has a dominant strategy, or is otherwise imperfect.