Well, every smartphone is also considered a computer. A computer is a device that stores and processes data, which is what a smartphone does.

So the PS2 ain't the bestselling computer of all time.

• iPhone 6 = 222.4 million
• iPhone 6S = 174.1 million
• iPhone 5S = 164.5 million
• iPhone 7 = 159.9 million
• iPhone 11 = 159.2 million

https://en.wikipedia.org/wiki/List_of_best-selling_mobile_phones

Fun fact, the Wii Remote has internal storage, and thus can store data (which the PS2 actually can't do, but I digress). It has a processor that is used to process data. 

As of 2010, 65 million Wii remotes had been sold in the US. Conservatively, we can figure that these figures reached at least 80 million for the US. The US accounted for about half of the Wii's total sales, so we can estimate 160 million Wii remotes sold worldwide.

So, there you have it, the best selling home computer of all time is the Wii remote. Of course that is a completely absurd statement, but that is where that rabbit hole leads. 

If that's your definition, then smartphones are the best selling computers of all time. 

See how having such a loose definition doesn't work?

The PS2 is the best selling dedicated video game console of all time. As for the personal computer, who knows? Compaq, perhaps? 

Not gonna lie this was an absurd argument to make on many levels. There are so many things you wouldn't consider a conventional computer that could be considered a computer if we go by definition like game controllers. Even home appliances like refrigerators and microwaves could be considered home computers which you could argue outsold the PS2, and even if the PS2 outsold singular hardware variations of these computers its pretty misleading to call the PS2 the bestselling home computer of all time since computers are constantly updating with slightly different hardware variations and being discontinued far more quickly than consoles, it doesnt at all mean people own a PS2 more than home computers that pretty much are used for the exact same function and OS despite having different hardware variations. There's just so many levels wrong in the argument in calling the PS2 the bestselling home computer of all time.

I'll just leave it as PS2 being the bestselling console of all time, nothing more, nothing less.

However, I will point out that Sony did call the PS2 the "bestselling home computer entertainment device in history". So the PS2 could have that title, as long as it's called a home computer entertainment device

Nah as others have pointed out, individual iPhone models have destroyed the PS2 and those have more of a claim as being a broad computing device (can run word processor, calculator, daily planner, various software programs on top of just games, etc. etc. etc.).

Is the Nintendo Switch the best-selling Calculator of all time?

I wouldn't call it a home computer but clearly it sold more than any other specifically model of prebuilt PC.

What makes the mobile phone list significantly more impressive is that each generation of iPhone is effectively one year, the PS2 generation was over 6.5 years, so it had more time than all those phones combined.

But even as far as proper computers go, I would say the C64's reign (at 30m sales) has likely been surpassed by some model. Looking at Apple's statistics from 2022 alone:

• 232 million iPhones, 61 million iPads and 26 million Mac and MacBook units were sold in 2022
• It sold 82 million AirPods and 53 million Apple Watches in 2022

Apple Statistics (2024) - Business of Apps

I'm guessing the top selling computer (proper) is some model of MacBook. And if iPads are considered, one of those instead. Should iPads count? Here's a modern iPad vs C64:

Nokia did some insane numbers back in the day. My first phone (3210) was a Nokia. I also had a 3100 (which might have been my third phone?), an N93 and N95 (8GB), lost count by that time because I updated my mobile about every 6 months to 1 year by that time (it was a different time, and mobile phones were way fucking cheaper). The N93 and N95 were both proper smart phones of the pre-iPhone era.