This is incorrect.
What is retro - what is old - are things that happened before my time. Things that happened during or after my time are not old.
So the Xbox 360, PS2, Dreamcast, N64, Genesis, and even NES are not retro, as they are not before my time. However, the Atari 2600, the Magnavox Odyssey, and the Mattel Intellivision are from before my time, thus making them retro.
It's a very simple formula.