Nikon D750 has a 24.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Expeed 4 processor. On the other hand, Panasonic G85 has a 16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . Nikon D750's sensor provides 8MP more than Panasonic G85's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the D750 and G85 sensor size comparison.
As seen above, Nikon D750 has a 3.8x Larger sensor area than Panasonic G85. 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.