All right this is one i have been wanting to write for a while but have not had the time to do so i will try to make this short.
First off i will be talking about both all age VN's as well as two adult VN's that are worth mentioning for their gameplay elements. First off lets start off by mentioning the gameplay element in VN's are choice think the Mass Effect choices taken to a whole other level when done right. The first game i am going to bring up is Steins Gate.
Released in japan for Xbox, PC, and recently PS3 this all age VN is one of the best examples of choice in gaming. With multiple endings this game will have you either looking up the walkthrough or drawing out a route map so you do not keep getting the bad end. Not to mention this game is about 20-40 hours long for a single playthrough if you listen to all of the voice acting and do not speed through it and it has very different endings unlike most games that offer multiple endings..... Mass Effect i'm looking at you.
From one VN that has some choice to a VN that has perfected it School Days HQ an adult game.
The website http://schooldays.us/
is the home of the game and is NSFW.
This game has the most endings i have ever seen in a game at 21 all very different from the last. To get them all you will need to play over and over and over at 60 hours i have gotten all but one ending. The entire game is animated first off and was the first fully animated VN that i am aware of. The endings are well varied very varied. First off there is no true end like in some other VN, there is multiple good endings a couple of harem endings and 3 bad endings that are well disturbing to watch and saddening.
From here i'm going to another Adult VN for this time more then just choice in gameplay Sengoku Rance.
I'm not going to mention the battle system in detail but with a picture for it'll serve a thousand words that i will never be able to convey.
To describe the battle system would take more time then i want to convey so i hope that picture helps.
Surfice it to say it not your average VN and is a exception to the rule just like the next game.
999 Nine Hours, Nine Persons, Nine Doors
For the best explanation of this game go to Destructoid
And thats about it oh and before it gets said not all VN's are pure sex games some are sure, but others have strong story's that are compelling and deep that are both all age and adult. And judging a genre of games on a certain subsection of that genre is retarded.
Well i think i kept that short sweet and to the point.