Unteralterbach is by far best erogame ever made, consistently high quality art at large quantity, well produced OST that's way beyond what you'll find in other games, best story in a game with funny dialogue all in 1 package. Shame f95 can't have its own page for it.
Sengoku Rance has good music, great gameplay and worthless animu art style. Since its such a good game on its own its still better than most games with actually arousing art.
Hizashi no Naka no Riaru is a uniquely good game with gameplay that can entertain you for hours if you decide to get every scene. If it wasn't uncensored by westerners it wouldn't be worth a mention though.
A dance with rogues is a module for neverwinter nights. The story is great and it's really long game. Since its a 3d game where you control your character its probably the most immersive porn game you can find.
Those are all very different experiences from each other and they're best examples of their type of games, and they're [Completed] too.