If you are looking for romance focused VNs, as seen in your examples, I suggest Symphonic Rain for a medium length and Ef A Fairy Tale of the Two for a long length. Kira kira is also ok if you want some music stuff. Da Capo and Da Capo 2 is on the ok-ish side but I won't place it before the three mentioned. If I have to pick only one, Symphonic Rain of course. The only downside is the resolution (640 x 480) of the VN.
If you want something that deals on society and stuff, you can play Sharin no Kuni, Himawari no Shoujo. Considering the ratings you have to G-senjou, I don't think this is the one you want but I'll put it anyway since I think it's pretty good.