Ruth Clark claims that "games don't teach," an obviously false statement. She has some legitimate points about matching the game design to the learning outcomes, but her claim that no research supports using games for anything other than "drill and practice" type activities is clearly incorrect. She makes this claim without addressing any work by Squire, Aldrich, etc., so it appears she didn't do a literature review prior to writing.

She cites one study with two games that were less effective at helping learners remember, and she believes that discounts the dozens of other studies on the topic. First, maybe those games were poorly designed. Second, if you're just measuring "transfer and retention" rather than application, I wouldn't be surprised that a game didn't do as well. Games are often better at moving from recall to application--but of course, she didn't measure application.