Umineko, as
>>555 says, was decent, ending aside.
Swansong was good, weird sex stuff and conspiracies aside.
Saya no Uta was good, loli sex aside.
Higurashi is apparently good, lolis aside.
Ever 11 was supposedly good, social scenes that drag out forever aside. (actually no it was just ass)
Chaos;Head and Steins;Gate were supposedly good, dragging out forever aside.
I'm not very good at finishing VNs.