Canon G16 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized BSI-CMOS sensor and features Digic 6 processor. You can shoot at maximum resolution of 4000 x 3000 pixels with aspect ratios of 1:1, 5:4, 4:3, 3:2 and 16:9. G16 has a native ISO range of 80 - 12800 and it can save files in RAW format which gives you a wider room for post processing.
Canon G16 is not the highest resolution Small Sensor camera. Kodak Astro Zoom AZ651 with its 21.0MP sensor is leading in this class. Check the comparison of Canon G16 vs Kodak Astro Zoom AZ651 or take a look at Highest resolution Compact cameras list.
Canon G16 DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Canon G16 sensor has been tested by DxO Mark and got an overall score of 54 for its image quality. You can find the details of their analysis of Canon G16 here.
Let's look at how the size of the Canon G16's 1/1.7" sensor compares with other standard sensor sizes.