If people want me to track visual novels not already included in the OP, give me a list of titles.
A list of titles that are significant or retail in Japan would definitely be relevant to this discussion, and the state of the ADV scene. They are also grouped by franchise:
Sekai Project
NEKOPARA Vol. 0 - 252,000
NEKOPARA Vol. 1 - 278,000
NEKOPARA Vol. 2 - 149,000
CLANNAD - 26,000
CLANNAD Side Stories - 2,000
planetarian ~the reverie of a little planet~ - 36,500
The Fruit of Grisaia - 25,500
The Labyrinth of Grisaia - 3,300
Idol Magical Girl Chiru Chiru Michiru Part 2 - 4,200
Root Double -Before Crime * After Days- Xtend Edition - 4,200
Visual Arts
Harmonia - 4,000
Tomoyo After ~It's a Wonderful Life~ English Edition - 2,800
MAGES.INC
Steins;Gate - 13,800
MangaGamer
Go! Go! Nippon! ~My First Trip to Japan~ - 171,500
eden* - 64,000
Higurashi When They Cry - Ch.1 Onikakushi - 62,400
Higurashi When They Cry - Ch.2 Watanagashi - 17,700
Higurashi When They Cry - Ch.3 Tatarigoroshi - 6,300
Higurashi When They Cry - Ch.4 Himatsubushi - 2,800
Umineko - 3,600
JAST USA
Flowers -Le volume sur printemps- - 2,800
Littlewitch Romanesque: Editio Regia - 4,200
Sonicomi - 8,400
CFK Co.
Princess Maker 2 Refine - 10,100