The term "grok" comes from Robert Heinlein's book Stranger in a Strange Land, and is a Martian term that roughly translates into "to drink," which also describes the Martian's take on the act or state of understanding fully--"to understand so thoroughly that the observer becomes a part of the observed." If you haven't read the book yet, you probably should, as this idea of grokking alone is worth grokking.
Typically, it is difficult to ascertain whether someone has grokked, or fully grokked, an idea--especially one expressed through art. Because artistic expressions exist outside the realm of language or even rational thought, there is no real way to test whether someone "got" it or not. It's quite common to hear the following conversation after a film:
"Didn't like it."
"But did you get it?"
"Yeah, I got it, but I didn't like it."
"But did you really get it?"
The ability to tell whether an artwork has been grokked or not is important for precisely this reason: that it is difficult to have conversations about art unless you know that your interlocutor has grokked it as much as you have. This works both ways. More fully grokking something does not mean that you'll like it more--in fact, it could very well mean you enjoy it less. For our taste to improve and to grow as people, it is important for us to know who grokked the work the best and what can be said about it.
Which ultimately brings us to the wonderful uniqueness of games. They have a built-in grok test (at least games as I define them). If you keep losing the game, you have not grokked it. Simple as that. To paraphrase Sean Connery in The Rock, losers whine about doing their best--winners grok the prom queen.
Now let's unpack that idea a bit. The simplest way to understand this concept is to think about gated games, which can be seen as a series of grok-tests. In fact, this I think should be thought of as the primary purpose of the gated games--not games unto themselves, but rather an interactive instruction manual that verifies the player truly understands how the game is meant to be played. We can say that once a player has completed a gated game, that the player has grokked the game--at least on that level of difficulty, if the difficulty is variable. While some may argue that there could be more to a game than simply its rules, I would argue otherwise, though I agree that many video games hold some elements in higher regard than their rules--to their detriment in my opinion.
A more interesting scenario is a game that involves human competition. In this case, we can say that while the nominal goals may vary, every game has at heart the same goal--to grok the game most fully. Therefore, when humans are competing in the game, the competition is to decide who understands the game the best. This is a fairly simple test--if I can beat you at the game every time we play, I clearly understand the game better than you do. The interesting thing about human opponents is that every time they are defeated by a new strategy, they have grokked the game more fully, so the next time you play them, you are playing against a stronger opponent.
This even applies to games that involve luck. As there is a point in luck-based games where the understanding of the rules will no longer assist in winning, it is at this point that the game can be said to be fully grokked. In part, this might relate to the "fun" of a game--that games are fun when the competitors have an equivalent understanding of how the game is played. Games aren't fun when you are out of your depth, and also when you have a vast superior understanding of the rules versus your competitors. Therefore, what I said earlier about chess and fun needs to be revisited, slightly--chess is a game that can create a large disparity between the amount one player has grokked the rules versus the competitor, which creates a situation that is not fun. Lotteries and other games of pure chance are easy to completely grok, so that it will not take long for a newcomer to have the exact same understanding as a seasoned pro. Therefore the difference between the two is the likelihood that you will have fun (i.e., compete against someone who has grokked the game equally), not whether one is flatly "fun" and the other is "not fun."
The beautiful thing is that this creates an reasonable grounds for authority. If I can beat you just as many times as you beat me at a game, we have equal authority in our opinions of the game. However, if I can beat you many more times than you beat me, I have a greater authority to deliver an assessment of the game, because clearly I understand it better than you. While this doesn't address things like disparities of aesthetic values and the like, it does at the very least address that first level concern many critics of art have, which is, "Do you really get it?"