"the last word on this is going to have to come from objective observers - for example, mainstream media outlets - not the videogaming industry."

Although I take your preceding point about the game industry's own bias, this statement strikes me as naive. Mainstream media outlets clearly have an overriding financial interest in "good", juicy news stories - which means that more or less hysterical claims about the supposed dangers of an activity engaged in by huge swaths of the teenage and young adult population are always going to be more newsworthy than a dull but accurate scientific report stating that nothing out of the ordinary happens with people who play games a lot. Don't expect the mainstream media as a whole to pass a more objective judgement on this issue than the more specialist outlets such as Edge.