Sometimes it's easy to lose perspective amidst marketing. Case in point: Nielsen measured that gamers, on whole, spent 31% of their time on the PS2 in 2008 (more than the Xbox 360 and Wii combined).
The other interesting, though not necessarily surprising finding was that the gaming population spends more time playing the 360 than the Wii, despite the 360's lower install base. Microsoft can probably thank Call of Duty 4 for that win (along with similar online titles).
One point we're not sure about, however, is whether or not portable systems were included in this list. We're guessing not, as the DS would have probably popped up somewhere. [Kotaku]