Both Nikon 1 S1 and Ricoh GXR S10 24-72mm F2.5-4.4 VC have 10.0 MP resolution sensors but Nikon 1 S1's sensor is 1" (13.2 x 8.8 mm ) and Ricoh GXR S10 24-72mm F2.5-4.4 VC's sensor is 1/1.7" (7.44 x 5.58 mm ).
Since Nikon 1 S1's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Ricoh GXR S10 24-72mm F2.5-4.4 VC.
Below you can see the 1 S1 and GXR S10 24-72mm F2.5-4.4 VC sensor size comparison.
As seen above, Nikon 1 S1 has a 2.8x Larger sensor area than Ricoh GXR S10 24-72mm F2.5-4.4 VC. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.