It might be the equivalent, but all PS3 games still run on a PS3, all PS2 games run on a PS2 and all PS1 games run on a PS1.
The PS2 was released five years after the PS1, and the PS3 six and a half years after that (I'm using the release dates for my location).
However, in the same time frame, you could buy a new PC in January of any year, and you'd already be having a hard time trying to run games coming out in December of that year, if not July or August, forcing you to upgrade. And because individual systems can be so unique depending on brands of hardware and such, even system requirements mentioned on game boxes don't always guarantee a smooth run. And if you're not a computer wizard who knows how to play with the settings and software, you're screwed.
To me there's a clear difference between a next generation console and a new computer with better hardware. Any fool knows you can't run a PS3 game on a PS1, or an X-Box game on a Wii for that matter.
That's why I switched to consoles back when GTA3 came out. If a next gen comes out, you only have to pay for a piece of hardware once and you're set for several years. I'm not one of the lucky ones who can buy a new computer each year to keep up with new releases.
Sorry for the rant, but I'm a budget gamer, which doesn't make me any less enthusiastic about games than people who can afford more than one system, and budget gamers to me seem a mostly ignored demographic, which is only natural because companies will always focus their attention on the people from whom they can receive the most money.