We all have fictional characters we would love to fuck, but it helps when they are drawn by good artists - some are great quality and others are garbage.
I gotta agree with davehytmen, But I do understand how people can be attracted to arguable "shitty art" like tram param (IMO) and such is because they haven't been looking at an excessive amount of hentai to get a real understanding of what is arguable good and what is not. I say this because I was the same way when I first started to look at hentai. Basically anything looked good to me, but as the years went by, I went to go look at the pics that I once though of as super great and though that they were kinda shitty drawing. What is shitty can also be very debatable, since I like artists like Gerph because of his thick art line drawing and bright colors, along with not trying to make it look realistic at all, but other people could look at his art and call it simple and shoddy. I still have to agree with davehytman with those fanchises, because I usually see those kind of franchises getting shitty hentai drawn for them (IMO).
I think the appeal goes for it on show standards is that the show is relatable for most people that watch the series, like real life problems how to deal with it, and so on, and as for the sex appeal, I guess since they add kinky moments here and there and natural pervs come at time it makes since for them to be turn on for it.
Seems like solid arguments. Personally I only seen a few tram param when I first started looking at hentai. Already disliked it to a degree since it, as you said, was lacking. Personally I could never see the attractiveness of American Dad, Family guy, or the Simpsons; yet when it came to iCame those images always got a high score.
I saw the image count of Pokemon and it was over 40,000 pictures because of the girls there were more pictures of Pokemon than Family Guy. I think people should click ICame images of Palutena and Phosphora from Kid Icarus, Glimmer, Mythra, and Pyra from Xenoblade Chronicles, Corrin, Camilla, Azura, Caeda, Byleth, and Lucina from Fire Emblem, the girls from Food Wars, Tekken, and Dead or Alive.