Depends on the age of the person. For me Retro is consoles older than NES like Atari 2600 e.t.c and pc consoles like Amstrad, Amiga e.t.c.

Graphics Wise Playstation 1 generation and older consoles feels "Retro".

Any system that is no longer supported is retro to me.

So that would start at 7th gen and older as 8th gen consoles are still receiving games, updates and features.

It ends on September 20th 2011. That’s the exact date.

When I saw "2011" I initially thought the launch of the 3DS, but that was earlier in the year.

What happened 20th of September?

IDK I think I was more making a joke or smth, as if there’s like a day in which everything changed. To give a bit more of an actual answer: I see games like Skylanders: Spyro’s Adventure, Just Dance 2012, and Call of Duty: Black Ops 2, and I see a retro game. Anything releases prior to PS4/XBO/WiiU is retro to me. Definitely a lot later than most in this forum, but that’s prolly just a consequence of me having been super young when those games released. I was only ten years old by the time PS4/XBO dropped, for instance.

The concept of retro is highly flexible. For me, anything from before the generation of consoles with 3D graphics is retro. It's a difficult topic, and subjectively, consoles since the launch of the PS1 and Saturn, with their distinctly animistic polygonal perspective, are more widely used than CD media.

There was a thread that called the Wii retro.  They called it vintage.  

Vintage, man! The bloody Wii!

I need a cloud to go yell at.

That was me; "vintage 2006" is just a way of dating something/indicating what time it hails from.

For the record, I don't really consider the Wii to be retro, I was an adult during that gen, so it still feels feeling "modern" to me. 

I would say 5th generation definitely qualifies. 6th generation I could argue either way.

It used to be anything two generations before.
So when Wii and the others came out, N64, PS1 and Saturn became retro.
Even with generations and cross-gen getting longer, I view Gen 6 as the newest retro generation.
Seventh generation hardware had tons of online features (especially 360 and PS3) which makes it tough to consider retro. Shoot, the 360 Marketplace finally closed in July 2024 and the PS3 Store is still open. It makes it tough to consider that generation retro.
I consider any game before late 2004 in particular retro. And I consider Gen 6 hardware retro. Gen 7 is getting really close to retro.