From Key I have read CLANNAD, my first VN, then Little Busters!, followed by Rewrite and last Planetarian.
From non-Key works I have got to read Symphonic Rain, a music themed VN shorter than Key words that revolves about a boy studying music, that must find a vocalist from the same school to team up for the next exam... of course, all the choices are cute girls, though there's quite some drama. Also, there's a fairy with him for apparently no reason.
And then... we have Higurashi no Naku Koro Ni and Umineko no Naku Koro Ni, masterpieces, I don't enjoy terror too much (I get scared too easily, lol) but the stories were just too good, though I guess that Umineko should be said to be a romantic story... (Without love it cannot be seen)
I also have played several Ren'Py short VNs, but nothing worth mentioning between them.
Umh... right, I also played Amnesia, my first time at an Otome, which was a bit weird... to be honest, I didn't like too much how the boys were drawn, but they weren't bad characters and the story was not bad at all, but the best was the anime's opening (lol).
Also... can I consider this VNs? Zero Escape series, I have played 999 and Virtue's Last Reward, planning to get Zero Escape 3 soon, sadly I don't know if my PC can run the Steam version, so I'll go towards the 3DS version once I save some money; they're some killing games styled, escape room based games, but half of it at least is pure Visual Novel and the choices there are what affects your ending, which there are many, and the story is awesome, with thematics of science and pseudo-science all around, oh, and maths. (I like maths, I know I'm weird)
There's also Ace Attorney, but I would say that the VN fragments there are less important, being the exploration and the trials more important, so I consider it just a videogame.
Also... I started Katawa Shoujo... but dropped it before I even finished a route, it felt too boring and uninteresting, I just remember trying to go after the burnt face girl...