Games such as GTA, Mortal Kombat, etc? I think you'll find that they have the opposite effect that they reduce intelligence.
Tetris, on the other hand, is not unlike the kind of problem you get in IQ tests, so I suppose playing could well increase intelligence.
I'm currently playing the Total War series of games: Medieval, Viking Invasion and Rome. Whereas there are no inherent educational qaulities to them, having to balance the many different aspects of building an empire and the mental workout that this entails could have beneficial effects on intelligence.
Which country makes the best films?