Yes, Yes I do.
Any "Sex Scene" showing two people reproduce, and shows full nudity, is basically considered porn. Which is NC-17 (it isn't X, officially)
In GTA San Andreas, you saw the woman full nude, in some parts (as poorly drawn as it was), and therefore it was considered "porn" (if you could get turned on from watching polygons)
In Oblivion. You could only see the women's breasts. Which I have seen in many rated "R" movies. Which is why it got slapped with The videogames equivilant of R.
So if you take it that way, it seems is that the videogame ratings are just the same as Movie ratings...At least over here.
I'm not sure about how you other people in other countries rate. But over here, It makes sense.
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