1700 + in another website

I am rated around 1500 in rapid here, in another famous website, similar to chess.com, I am rated 1700+. We have probably much more people playing here, right? 

That probably has little or nothing to do with the difference.

But it doesn't matter.  Ratings aren't measuring anything absolute, like the temperature that water freezes or boils.

They just predict how you will do against others on that site using that time control.

/ One factor is that different sites use different starting points.

I'm the same torrubirubi...rated rather better on that "other" site...I still suck completely though, of course

The asparagus I'm baking in the oven, has a better rating than me at the moment. So 1500-1700 tomato, potato.

Yeah, many other sites have inflated ratings. This website has a rating which is pretty consistent and comparable to Fide ratings. The large pool produces the consistent ratings which are discernable between 1600s and 1700s etc. My USCF is 1900, which is probably 1700 Fide, which is close to my blitz. The blitz ratings tend to be consistent here with Fide ratings.