The PS3 vs GameCube sale equivalence is about right if you limit your data to the USA.
But WW sales look entirely different.
In general, I really can't understand where the meme about PS3's so-called "horrible sales" or even "failure" comes from... the PS3 is not storming the market but is selling well enough against consoles that
1) are much less expensive up-front (in price tag terms)
2) are much better advertised
3a) had a whole year to estabilish a foothold in mindshare and advance in game quality (Xbox 360)
or
3b) cater to a different and much wider market (Wii)
In particular it's selling better (at equal time from release) than the cheaper x360 that is its most direct adversary in its market niche.