DxOMark: Is the 75 1.8 the best m43 lens Available?

They are roughly comparable for the reason you mention. If you want to be perfectly accurate, the figures for the Leica should be multiplied by 1.08 due the difference in aspect ratio (4:3 versus 3:2). On the other hand, the Leica is advantaged by its slightly higher pixel count and (more importantly) lack of AA filter, which may well mean that it cancels out.

Leica lenses are certainly good. But the Summilux is about ten times the money and the M9 more than five compared to what you have to pay for the 20/1.7 and the E-M5. So the performance-price ratio of Leica equipment is rather questionable.