The consoles you grew up with are now officially retro. GameStop, the world's largest brick-and-mortar video game retailer, announced Monday that it's labelling multiple seventh- and eighth-generation home gaming consoles as "retro consoles." The Xbox 360, released in 2005; the PlayStation 3, released in 2006; and the Wii U, released in 2012, are now "historical artifacts" of the games industry, according to the retailer. It's hard to define the "retro" label in gaming circles. There's a fierce debate over whether the transition from 2D to 3D graphics, the rise of online gaming or the adoption of digital audiovisual outputs should qualify consoles for the designation. What matters most is that the definition of retro gaming is fluid, and GameStop has set forth its own criteria for redesignating these three home consoles.…