With an estimated 155 million units sold worldwide, Sony's PlayStation 2 is the most successful console in video game history. The system also had amazing longevity, with the first units produced in early 2000 and the last ones rolling off assembly lines over a decade later in late 2012.
A number of factors contributed to the console's unprecedented success. It built on the momentum created by the original PlayStation, which was extremely successful at capturing the then-emerging market of adult gamers. And though the Sega Dreamcast was technically the first into the 128-bit generation, the PS2 was hot on its heels and represented a significant upgrade in hardware capability.
It was also the first to use DVD media, which proved to be extremely successful from a marketing standpoint during a time when a DVD player was a significant added expense for most families -- Sony offered buyers their gaming and their movies all in one device. The inclusion of the DVD player also helped to legitimize the console as something that adults could leave out in their living rooms, instead of tucking away or hiding in a basement or kids bedroom.
One of the big marketing points during the early period of the PS2 was the "Emotion Engine." This was simply a nickname for the console's central processor. It was an innovative and powerful design, optimized specifically for 3D gaming. And like the PlayStation before it, Sony went out of their way to make it friendly to third-party designers.
Of course, hardware and marketing alone can't carry a console. Ultimately, it lives and dies with its lineup of games, and the PS2's library of over 1,800 original titles is arguably the strongest overall in gaming history. Just about every genre imaginable has at least a few hit titles. While the 2000 launch was middling overall, 2001 saw a string of landmark titles released that really cemented the PS2's competitive advantage: Grand Theft Auto 3, Gran Turismo 3: A-Spec, Metal Gear Solid 2, Final Fantasy X, Jak and Daxter, and Crash Bandicoot: The Wrath of Cortex being the biggest of the bunch.
And though there really weren't any concrete plans for them when the console launched, the included USB and Firewire ports also turned out to be a great move. The Guitar Hero and Rock Band series would turn out to be gigantic sellers. And while devices like the EyeToy ended up finding more of a niche market, they would lay the groundwork for the mainstreaming of similar camera-based and motion-controlled systems in the next generation of consoles.
The PS2 saw several different form factors released over its lifetime, but the two main variants are the "fat" and "slim" cases. The slim case varieties were first released in 2004, and trade the hard drive expansion bay for significantly less weight and a lower profile. It should be noted the expansion hard drive is required for a handful of games, however, including Final Fantasy XI.
Ultimately, the PS2 ended up being a console that really had something for everyone, no doubt a major contributing factor to it being the best-selling in gaming history. Just about every genre you can think of is deep with good-to-great titles, and it's a lineup that retro enthusiasts could literally spend the rest of their lives exploring. Though there's extremely few areas where you can go wrong, some of the console's particular strong points are Japanese RPGs, sports, racing and open-world sandbox titles.