Retro-as-a-style used to be the ONLY meaning of "retro." It was something new that was made to look old. When it comes to games it usually just means "old" now. I personally consider the 360 and PS3 to be not retro because the general conventions of how they control and the way they were online and capable of getting updates is pretty much identical to today. They're old, all right, but other than having less polygons and post-processing effects they're not different enough from the games of today, as you said. The Wii is something of an anomaly and different enough that I'd consider it retro.