Both Canon S120 and Fujifilm XQ2 have 12.0 MP resolution sensors but Canon S120's sensor is 1/1.7" (7.44 x 5.58 mm ) and Fujifilm XQ2's sensor is 2/3" (8.8 x 6.6 mm ).
Since Fujifilm XQ2'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 Canon S120.
Below you can see the S120 and XQ2 sensor size comparison.
As seen above, Fujifilm XQ2 has a 1.4x Larger sensor area than Canon S120. 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.