I dunno what apple uses, but that's the two you see most around Google, default for docs, most of their sites use Arial. Roboto is the main one used on Android now, used to be Droid Sans.

Oh yeah, Noto Sans is another quite common one, because it has all the asian characters in it, they call it No Tofu, a references to the popularity of this soybean based rubbish that asians eat a lot of, as it's often sliced into cubes before frying, like the square placeholder characters used by fonts that don't support asian unicode.