Some people seem to confuse past statements. PS3 back then was compared to PS2 because it sold far less than its predecessor, that´s why people said it underperformed. What did PS2 sell in 6-7 years? 130m-140m? Compare it to todays PS3 userbase (6-7 years = 75m) and you understand what the topic actually was about.
That PS3 would outsell X360 was a widespread consent early on, it is actually quite more surprising that even after 6 years PS3 didn´t achieve this yet.







