So, do we even need them? I'm starting to think no. There's plenty to be learned from "real" games. The students in my gaming club have been having playing Warcraft III, an older game that stresses tactics and strategy. While my students work in teams to battle one another, they are forced to juggle several factors. They have to manage inventory, make value-based decisions about how to spend their resources, communicate with their teammate(s) about how and when to launch attacks. The whole time they're making these decisions, they keep a mental image of the massive map in their heads. It gets very complicated very quickly.
Of course, this particular game is also full of simulated violence. The point, though, is that the technology exists for us to create truly immersive experiences for our students. Take out the "assassin" part of "Assassin's Creed," and you have one of the most powerful educational tools I can think of.