NGL, I don't feel like the Xbox 360 or Wii are really "retro". A lot of the games still hold up decently well from a visual standpoint imo. Obsolete? Sure. Old? Sure. Retro? Nah.

I think the GameCube generation is the border of "retro". That's where you still had some games that looked old (like Animal Crossing), but you also had games that still look relatively good (like Pikmin). Imagine calling Crysis "retro". That's the same generation we're talking about.

I'm also saying this as someone who remembers the N64 fairly well.