Its well known that the PS2 had some major quality control issues early in its cycle, but those are long since past.
PS2s have probably broke down more over the last 3-4 years than Gamecube and XBox, but then again, consoles are less likely to wear out when there's no reason for anyone to use them.
The system that PS2 passed to become the #1 best-selling console of all time probably had more repurchases than PS2. Going from the original brick to Color Game Boy to Game Boy Pocket to Game Boy Color certainly resulted in millions upon millions of repurchases from existing customers.
Bottom line: PS2 is now officially the most successful console of all time. Too bad people see this as a Wii/DS topic.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
