I was disappointed to see my new favorite "pure" game Arimaa missing from Bostrom's list. Arimaa was designed to be intuitive for humans but difficult for computers, making it a good test case. Indeed, I find it to be very fun, and computers do not seem to be able to play it very well. In particular, computers are nowhere close to beating top humans despite the fact that there has arguably been even more effort to make good computer players than good human players.

Arimaa's branching factor dwarfs that of Go (which in turn beats every other commonly known example). Since a super-high branching factor is also a characteristic feature of general AI test problems, I think it remains plausible that simple, precisely defined games like Arimaa are good test cases for AI, as long as the branching factor keeps the game out of reach of brute force search.