Do you know anything close to your description?
Those I can think of are mostly story-focused visual novels or anime, not porn-focused games, for example Grisaia no Kajitsu, Muramasa, Baldr Sky, Majikoi, Classroom of the elite, Konosuba, etc. Among porn games, probably Funbag Fantasy to an extent, though there the MC is just a pervert who doesn't care that much about romance. The Last Sovereign is a great example, but again, porn isn't that big of a focus in this game and its art is kind of meh. Once in a Lifetime is good in this aspect, most likely Eternum is as well (I didn't play it yet), but those are S-tier must-play games in general, anyway.
I mean, it kind of makes sense that among Japanese games it's rare to see a decent protagonist, as many Japanese men are "vegetarians" as they are called in their slang (beta males in English), so their protagonists are usually either loser self-inserts, or rapists who're just an outer representation of the revenge of the timid "nice guys", i.e. rebellious losers.
Western games are probably better in this aspect, but they are often on the "thirsty" side of things. Plus, I'm not really into 3D CGs, most of them are kind of on the edge of the uncanny valley for me.