they really didn't though, those are on premium cable channels, and again, not restricted like most channels are. it makes more sense to compare what you see in an r rated movie vs an unrated movie, as cinema has a more standard and analogous rating system.
we can already do GOT level sex and nudity anyways in games. People are asking for straight up porn though.
Premium cable before these shows was something totally different, they set a bar, and in doing so changed the TV industry.
Different Porn companies do work on different forms of porn, you some companies like Brazzers that stick to pretty basic porn plots. But there are companies and amateurs that focus on something more natural and tasteful. Without getting into the details, the focus of these "natural" shoots is on the connection and enjoyment. In the same context, games focus on doing both, you have God of War style stuff and you have TW3 style stuff. Porn is a very very large classification of media. There are all types.