I recently picked up a Stern PoTC and thought that one has rules that are in the sweet spot: not too simple, not too deep. The rules card is amusingly vague, but it reflects that you can learn the game by playing it. I appreciate that in a game. But I can also appreciate various depths of rules too.
I think an interesting question would be, how many times do you have to play the game to learn 90% of the rules. Difficult to say all rules, because getting to a wizard mode that has special rules would skew that too much. This is actually something that might not be that far-featched to measure as there's now AI-playing systems that pretty much do this.