I think it's about much more than just the art style.
There are 3D games I think look great (like
Tresure of Nadia), others not so much (e.g.
Neko Paradise). Sometimes the models are fantastic, but the animation is terrible, and that can also kill it for me. (I wish more people just made slideshows when they can't animate.) I haven't played
Being a DIK or
City of Broken Dreamers, but I think they look really good. My biggest problem with 3D games (besides animation) is that breasts often end up looking fake as shit (compare the characters with bigger racks in Treasure of Nadia vs. the ones with more realistic sizes).
Also, clothing sticking tight to the curves of the models instead of drooping realistically, but that's more of a pet peeve.
I like Western cartoon styles in general, but all too often they either go very heavily into a stylization which doesn't appeal to me (e.g.
Queen's Brothel—which I used to like a lot more before they redid all of the art), or exaggerate proportions to ridiculous degrees (like half the characters in
Trials in Tainted Space). If I look at the three games you listed, I think that
What a Legend looks great,
Taffy Tales would look pretty good if it weren't for the titanic bust sizes, and
Summertime Saga looks rather unappealing.
I'm a big fan of anime style. They can also be prone to exaggerated proportions, but I think both
Monster Girl Club Bifrost and
Discipline look great.
Monster Girl Quest and
Rance look good too, though they're maybe a bit too
moe for my tastes. The reason I usually don't play them as much has nothing to do with art: looking through these four games you've listed, I see urination, prositution, rape, scat, etc., coming up several times. I might love the art, but Japanese and anime-style games frequently feature a bunch of tags I like this which I absolutely abhor.
Honey Select also has varying levels of quality. I think it looks pretty nice in general (
Once in a Lifetime), but like the cartoon styles above, I feel there's a tendency for proportions to be exaggerated beyond what looks good (IMO), as is the case with a couple characters from
Pale Carnations and
Harem Hotel .