I only played a few of the games list, but i try to share my experience and thoughts why the games will be vanished (forever?).
•Kanpani Girls:
Never played. Maybe cuz i hadnt the time to test it.
•Shooting Girls:
Lol now its a bit of embarassing cuz i didnt notice there was a game like this. :/
•Quiz of Valkyrie:
I have this game. To be honest, i was really warm with this game cuz those quizes was smtimes a mess up for me, so smtimes i had problems to figure out what i have to do. I think the idea of this game isnt bad at all, but my guess some things was to confussing for some ppl that they forgot this game over the time.
•Angelic Saga:
Before i played Millennium War Aigis i started Angelic Saga. I had a lot of fun. The events are good, the story isnt bad at all, easy farming (for me) but i think i know why ppl went over the time and wont pay anymore. The problem is that "Online-Torunament" meanings play against other players. I played a few times against other players and i noticed 2 things: One is the players itself. There was some players who cashed a lot to made the "perfect" decks to beat everybody in a few rounds. So there wasnt to much fun at all. the other thing is, smtimes you will kicked automatically from a match. I cant say if it the connection or the game freezes. However i enjoyed this game a lot and collect a lot of cards. Would be sad if it must go. If they would updating the game, im sure many players would come back.
•Hitsuji Chronicle
Never played before. I would but i kinda forgot :O
•Omega Zodiac (already discontinued)
Never played before.
•DDTank 3
Never heard of.
•Hellfire Girls
I played both versions. I played the asian version more than the us version. Of course the asian vers has to much censorship but there was interessting girls However both games are identically the same and i was bored cuz the events wasnt so good. The pics and so are interessting but the game itself was so boring
•Girls Kingdom
I also have this game. I had a lot of problems in this game cuz i had to figure out how to play exactly and i failed way to often. The chars looking good, but that building things was a mess up for me. Smtimes it was to much chaos that i didnt know what to do next etc.
•X-overd
I have this game, but i was always to lazy to play. Evene the girls looks interesting. But i cant say why this game must go.