You're definitely right about the least realistic material in pornography being the most popular. For example, "hentai", which is animated pornography (frequently rape porn involving underaged school girls with impossibly gigantic boobs being attacked by monsters, aliens, robots, animals, gangs of men, etc.) is the fastest-rising category of pornography at present, and currently the second-most-searched term on Pornhub (the leading online pornographer) after 'lesbian'. In fact, it's the #1 category among teens and college-age youth now. You can't get farther away from reality than that, where characters commonly have boobs bigger than their faces, dicks the size of small buildings, and the scenarios are typically the most brutal and blatantly misogynistic in all of pornography, involving all manner of illegal activities (rape, children, mutilation, bestiality, etc.) and stuff that's physically impossible.
Where we disagree is in the idea that people's preference for highly unrealistic material is somehow a good thing. Consider that there is now a whole generation of people who's first, and perhaps only, form of sex education has been exposure to this sort of material. That clearly has negative affects in real life. In addition to producing serious body image issues among both men and women alike, you're also seeing consequences of it in the increasing commonality of practices like anal sex that are fun for men, but painful for women, as well as women (especially young women) being involuntarily grabbed by the throat and choked during sex, and so on and so on; practices that young men are clearly learning for pornography. And it's demonstrably resulting in the women especially becoming less interested in even having sex at all; you're seeing a trend away from sexual activity altogether that's being led by younger women. (
See point 4 here.) Is that really a good thing?