Yeah, this is one of those things that gets a lot of people seriously up in arms.

Classic cars, for example, are defined as ones that are 20 years or older, or if they have some particular significance. I think that can generally work for games as well. Some might bristle at the idea of the OG xbox and PS2 as retro, but they're both pushing 25 years old at this point. Which is why I think it's generally an ever-moving line. But it's also one that can often be subjective. My first game console was an NES. But someone else's first console might have been a Gamecube. So our frames of reference are going to be different.

I think it's also challenging when a lot of older games are still playable on modern hardware. There's a ton of games that were released for the OG xbox that are still playable on the xbox one (not sure about series x|s): Morrowind, Halo, KotoR. Since we often think about retro games being ones that are out of production and difficult to play in modern times (like the difficulties with connecting an NES or an Atari 2600 to a non-CRT TV). But backward compatibility has shifted that window for a lot of titles. Which is why I think a lot of people balk at the idea that an xbox or PS2 might be considered retro, even given their age.

So I think it's really a matter of relative time + a healthy dose of subjectivity