In this case, a study population played the game Rise of Nations. After a while, they showed improvement on cognitive tests. This tells us what we already know - that complex tasks involving repetition and especially multi-tasking which demands a recurrent loop of attentiveness load can extend the boundary of cognitive ability.
Unless the specific variables of the game play map to quantitatively measurable scales of assessment, and this assumes that a set of qualitative or social choices with a very large and tenuous possibility frontier and unknown internal verisimilitude can be expressed mathematically, it's difficult to take the conclusion beyond the initial mild statement. Nolan Bushnell could just as easily have said that Pong was brain-boosting, or the video-disc game dragon's lair (the first anime-style game [no sprites] that could be controlled from a console) boosted the brain while the gamer waited for her/his pizza to get ready.
However, this means that more rigorous and focused studies of populations that already have been published exhibit that much more potentiality and promise. Our exploratory work with professional gamers (2005) exhibited as much.