I am digging through my growing stack of research:
Katz, L. (1999). Another look at what young children should be learning. Champaign, IL: Clearinghouse on Elementary and Early Childhood Education. ERIC Document #ED430735.
The Katz article doesn't discuss video games, but does provide a set of criteria that any children's learning activities should be judged. The four criteria needed for promoting learning are:
A successful game does try to reach the player on all four of these levels. A game does teach the player skills: from higher level skills like critical thinking & planning to practical skills like time management & reaction. The challenge of parents and educators is to try to connect these skills to the world and education.
Knowledge is gained by the player through the trial, failure, and success of the gameplay. What that knowledge is though, depends on the game. But the process of learning and gaining that knowledge (even game specific) is important.
I game can change a player's disposition, depending on the seriousness of the game's content. Serious games & persuasive games (like The McDonald's Game, PeaceMaker, or Food Force) attempt to change the players understanding and viewpoint on a specific subject.
Video games try to evoke the emotions and feelings of a player. Whether those emotions are tension and adrenaline or aggression or compassion and empathy, every video game is designed to connect with the player on some level of feeling.
So, yes, according to Katz's (1999) criteria video games are activities that promote learning. Okay, that thesis is not new, but Katz's criteria provide another useful perspective in defining how video games assist in the learning and development of children.