Here's the Nokia 808 PureView's sensor and ribbon assembly, shown next to local currency and a typical 1/3.2" sensor from other top smartphones (e.g. Lumia 920, Apple iPhone 4S/5, Samsung Galaxy S III, HTC One X):
Quite a difference.
Just for comparison, while we're talking links of interest, here's a handy chart showing the relative physical sizes of various sensor 'optical' sizes. In the chart, the bright pink section is where all non-Nokia smartphone cameras are right now, the pale pink (1/2.3") is where the 2009 Nokia N86 was, the 1/1.7" band is close to where the 2010 Nokia N8's camera sat, and the 808 is labelled on the chart itself:
(image credit: DP review)
Which is not to say that other manufacturers haven't made strides in other areas - the near universal use of Back Side Illumination, for example, but it's clear that Nokia's cameras possess a physical advantage here that is rarely overcome by the use of BSI and larger apertures. Remember that light gathering and detection is relative to the square of the physical sensor dimension, critical when in challenging light situations.
Here's another image from the Mobilport article, showing the old Nokia N93 'barrel' camera module, plus the completed 808 PureView camera module, next to the sensor itself: