Kana -Little Sister- tops my list because of engrossing story and quality graphics. I agree with what others have said about this title being just as good without the H-scenes. Wish we had a few more like it.
I also have a warm spot for True Love. I think it’s a great combination of love sim and graphical novel and haven’t seen another game quite like it. It was my first bishoujo game, and I admit I had to get it from an abandonware site, but I’d gladly buy the CD if it were still available.