Nah, Saya no Uta is the obvious "Eva of VNs." Practically mainstream, only slightly below things like Fate or Steins;Gate in terms of visibility, and infamous for being really weird, despite being pretty straightforward with some surreal imagery and a fantastical concept. And it's the VN that everyone will compare any other VN to if there's any sort of overlap, like supernatural horror or an immoral protagonist.