Game Per Cubic Inch
Or "Game Per 16.4 Cubic Centimeters".
I commented on BGG the other day about In the Shadow of the Emperor--a personal favorite with a great online implementation. It struck me that some games just have small boxes, but a lot of game stuffed into them. Of course, many wargames fall into this category, but I don't think a ton of euros do.
Of note, In the Shadow of the Emperor, Struggle of Empires (and perhaps some other Wallace designs like Perikles), Louis XIV, and Intrigue come to mind, which I played last night. It's not simply game length that I am talking about, but also complexity and immersion. Judging by size on the shelf, and not knowing any better, one might misjudge some of these small boxes.
What are some other games that might qualify?