The more imaginative the better, I'd say. The success of Big Brain Academy and Brain Training round here would suggest that there could be a massive market for more traditionally educational games.
(Not that we don't think that the problem solving involved in most platform games is not incredibly educational! And as for reaction times, I can't find the source but my guess is that it's all true that only 14% of the population could have passed the reaction time test for fighter pilots in the 1940s, when over 40% could nowadays.)
As to video games causing raised levels of aggression, I think if the phenomena does exist, it is only extremely temporary, being merely a product of being sped up and ready for action. It is anyway perfectly subject to will. The same symptoms can be generated in attempting to do any task that requires quick and close attention, such as IQ tests or quick maths problems. It is not confined to games and they should therefore not be demonised.