This is one of the reasons why the review process is so hard for Apple to get right. Apple has to make sure that every application not only doesn't use private APIs, but the applications must be legal in every jurisdiction that the iPhone is sold. That's likely the reason for not allowing nudity in App Store games even when Apple does allow movies with nudity in the iTunes store.
Movie studios create international versions of their movies. Movie studios have the budget and the motivation to tailor their products for multiple targets and to make sure that their movies do not violate any laws wherever they choose to sell them. Movie titles are often changed in translation to avoid trademark problems or to avoid offending the predominant culture in a specific country. Different versions of the same movie often have different scenes, sometimes with certain scenes available in the U.S. release being cut or altered in the version released for some other countries. In some rare cases it goes the other way, and a scene that the MPAA forces a filmmaker to cut or alter, is kept in releases for countries who don't share some particular taboo or social more with the U.S.
When you realize the true magnitude of the problem facing the app review team at Apple, it's hard not to cut them a little slack. Well, unless one of your apps happens to be stuck in review at the moment, in which case it becomes considerably harder to cut them any slack since you are being directly impacted.
So, anyway. Apparently, America is not the only country with asinine IP laws and large, soulless corporations willing to wield those laws as a weapon to protect profits.
I don't know anything about German trademark law, but if Ravenbursger's claim has any merit, this could lead a whole slew of new written or unwritten rules about what can go on the App Store. I don't see Apple taking a fine grain approach and removing offending apps from, for example the German store, but leaving them in the others. It would add considerable complexity to an already difficult and thankless job. It's not going to happen: They're either going to tell Ravensburger to stuff it, or they're going to remove every possibly infringing application from all app stores.
In US trademark law, Ravensburger's claim would likely not get very far. Although there are some exceptions, in the US, it is not possible to trademark generic terms. Certainly, this game has existed, and has been called "Memory" (for that's about the only skill it requires) since long before Ravensburger started selling lame licensed character variants of the game.
Does anyone have any idea whether this claim has any merit under German trademark law?
It is unfortunate, especially for the small, independent business, that doing business internationally is such horribly complex thing.