The high MP counts allows you do downsample/pixel bin for higher quality images and also allows room to crop, providing a digital zoom which doesn't suck.
If you are a big DxOMark fan, you'll find the RX100mk2 scores a 67, while the RX100 scores a 66, which is the same score as a Canon 7D's sensor.
And while you may argue that the 7D's sensor is old, Canon's been pumping variations of the 7D sensor into all of their recent APS cameras short of the freshly announced 70D.
To your point, I agree. I've seen comparable (and sometimes higher) IQ from my RX100 than I do from various MFT and APS-C DSLR/MILC cams with their kit lenses including the Canon T3i and T4i, GX1, a few NEXes, and Nikon D3000-D3200. The RX100 fares well against those cameras at the wide end of the zoom range when it comes to low light performance and thin DOF as well. Of course, you could spend more and get better lenses for those cameras and beat the RX100 in low light.
I do hope that the new sensor in the 70D provides an actual improvement in ISO score if not IQ and isn't just the older sensor with OSPDAF added.
I was just adding to the point about 1" sensors actually being as good as an SLR sensor, which they are.
Of course the RX100's optics limit some of its performance, but Sony's 1" sensor and the M43 sensor they sell to Olympus punch well above their weight, equalling or besting some existing APS sensors on the market today.