Well, few games are really banned in Germany. Most games on the index can be bought, they just can’t be marketed.
Games like Left4Dead and Dead Island are on the index in Germany not because of the level of gore in the game but because they contain some kind of virtual necrophilia which is against the law in Germany. Yeah, you heard right, it’s weird but that was the argumentation of the institutions.
Games like Chivalry which offers quite brutal and gore-intensive medieval combat are not banned in Germany.