Light of my Life .....great characters, good graphics and a the Ren'py coding is great. All in all, a well constructed game ........though probably not complete yet, oops!
I don't know if it's actually the best I've ever played, but Parental Love is definitely very, very high on the list. It was one of the first ones I completed, and I just loved it. How it would hold up if I were to replay it now years later, I'm not really sure.