There is difference between eroge(or nukige) and adult themed visual novels now just because there is sex in it it doesn't mean porn game for example Fate/stay night,the shell,devils g string and many that is considered masterpieces by many all this problem could've solved easily if you can read but guess you don't have that ability
The problem is looking at tags/names and not observing the nature of those scenes. I'm not talking about fate or anything alike, but there's a clear distinction between erotism and pornography. Most VNs could do without the pornography and the story wouldn't change, for example. While erotism is as important as tragedy would be in a drama, but it still clearly differenciates from pornography even if they share the same importance in the story. It's commonly accepted there're limits to how explicit can a sexual scene be. Most agree that if the erotism is perverted into fully shown and indulgent sex, it becomes pornography.
Madame Bovary is a novel that uses erotism as one of its strongest themes, while Hero Party must Falls is a pornographic visual novel, which is very erotic.
Obviously there are no rules to how well-written it can be, absolutely a porn novel can be better than a regular novel, even if it's less transcendent, after all porn satisfies a short and intense emotion that doesn't stay with you once you've had your fill.
And the main problem will always be (at least for me) that the writing needs to be dumbed down in order to make things work in a pornographic setting. It becomes too shallow and the purpose is too insignificant. But well, that's the point.
And I'll bet people appreciates fate's art and writing, but only is interested in the sex scenes once they're horny. This won't happen with erotism, since it builds sexual tension in a complete different way, in a way that stays with you and can be relived without the need of any urge, just like you would fondly remember how snow white and her prince shared their first kiss.
In the end, pornography does change completely the nature of a work, we can't deny it whether you call it adult novel or whatever.
