Love Hina and Negima.
At the time of reading I had a huge crush on Motoko and wanted to see a story with her and Kentaro. Later my crush sorta shifted to Kanako, so same thing.
As for Negima, all romantic relationships cut off at the same point and stayed in limbo with the "I'll wait for him to decide" state... I realize you can't keep a harem status by have a decision made, but it stop's being romance if nothing really changes... One of the things about harem (anime and manga) series I don't like.
The Gunparade March (manga) by Hiroyuki Sanadura would have been both a better anime and VN than "Muv-Luv: Alternative" (and whatever the anime was titled) with the subject matter and execution, to me.
Mai Otome (manga) by Satou, Kenetsu and Yoshino, Hiroyuki is the best "Mai..." series, to me, the only one I've enjoyed till the end. And I would have greatly loved for it to have not landed on the "harem end". As a Sim I would greatly enjoy it.
I know Ai Yori Aoshi by Kou Fumizuki is already a VN, but he is currently working on another series by the name of Umi no Misaki which I feel would better fit a visual novel format, considering the authors indecisiveness. Though I wouldn't say I really "want" it to be, just a thought that floats around my head.
Hanaukyo Maid Tai... Seen every reiteration of it and read most of the manga, I very much like Konoe, so the series drives me crazy with the cock-teasing "unrequited love development".
Either story from the series Gacha Gacha (manga) by Hiroyuki Tamakoshi have really interesting concepts that would make for a very interesting game story.
Yubisaki Milk Tea (manga) by Tomochika Miyano, would be interesting to have some extent of control in the proposed scenario, I'd be able to better identify with the protagonist struggles.
High School Host Club, would very much like to see Haruhi with the twins.
Loveless, based off the story of the manga by Yun Kouga, would be something I'd be interested in reading/seeing.
I might have been able to enjoyed Sekirei as a VN... probably not if I had to play as the stories main...
I've played a number of Yuri VN's, but none of them nor any anime since have ever struck me as interesting as Kannazuki no Miko. I realize a lot of nostalgia and a very "young and new to.." mindset has a big influence here. But no story since has ever made Yuri relationships into anything more complicated than "being without the person for a day or two". There are 2 manga's I can think of, one adapted into an anime that I missed (I need to watch it), but that's about it. None of them were interesting in the same way as Kannazuki no Miko.
I'd like to see Clamp make a couple of DatingSim.
Working! wasn't enough from the anime, I want to see post-"beginning of relationship".
Servant x Service wasn't enough from the anime, I want to see post-"beginning of relationship". Or just a plain dating sim by the writer of the 2 series, I like his take on romantic stories.
To Love-Ru was all over the place with fan-service for the sake of fan-service and additional characters, to me. Would have been better if it was just told in a VN format, allowing the writer to show off his characters and allowing the players to focus on the ones they were interested in. At least, that's my opinion. I may have enjoyed it if it was in VN format.
Haiyore! Nyaruko-san Fuck Mahiro and fuck the "Harem-end" with a rod.... I wanted to see Nyaruko genuinely obtain the only thing she spent 2 seasons struggling to get even a little bit of...
As much as I enjoyed the characters and story of Sumomomo Momomo in the way it was, I liked the other 2 female leads a bit more and would have loved to see those characters romantic interest realized.
Seto no Hanayome Somewhat similar to Sumomomo Momomo, but I very much liked the lead female character, just different takes at the story by the same people would be incredibly interesting and entertaining for me.
Maburaho... Nostalgia...
Rosario Vampire THIS ONE!!!! DEFINITELY THIS ONE!!!!
Magikano... Nostalgia again, but I did enjoy this series and know I would more as a VN.
I may have been able to enjoy Zero no Tsukaima as a VN, that way the focus wouldn't have been all over the place. The second season is where I felt it should have ended.
Amaenaide yo!!, I think it would have done pretty well as a VN. Not really a want.
Ichigo 100%... NOSTALGIA!!!
He is My Master... Nostalgia >_>
Fight Ippatsu! Juuden-Chan!! the series lacked the romantic progression I wanted/waited for, I demand justice!
Ladies vs Butler if it's not already a VN, it really strikes me as a series that should have been. I would have only been interested in the 2 female leads tho...
Koi Koi 7, Nostalgia! The anime was ridiculous and the manga was... it had it's high and low points. An individual story focusing on each specific character and a over-arching main story would have told the story better, imo.
Kampfer so much "want" in this, Shizuku!
All Masaki Kajishima works (Tenchi, Dual, Photon, Spaceship Agga Ruter), for reason I shouldn't have to explain.
Ore no Imouto, because the anime trolled me... Last min, "ya, lets give up our (now fake) relationship and everything we sacrificed for it" before the show ends... Tho as bitter as I am, maybe not... >_>
Boku wa Tomodachi maybe... Would be better suited to the VN format. I like Rika... Hated the running gag the author made Sena into, especially since I liked her.
Nagasarete Airantou should have been a VN, I know I would have enjoyed the "romance" elements of it this way.
Inukami so much want in this.
Yamato Nadeshiko Shichi Henge want.
Namiuchigiwa no Muromi-san this should have been a VN from the start (assuming it's not).
Hataraku Maou-sama! I would have been able to enjoy this series to the end, as a VN, maybe. Seemed as if it should have been in a game format anyways.
Golden Boy Nostalgia... That and, I hated how wacky and spiritual the story became after vol 6 or so. If the writer wrote it all at once, maybe it would have been more collected.
The World Only God Knows, how can I not mention this... it screams "make me into a vn" so very hard...
Nisekoi, because these kinds of series always makes me invested in the character who is not the main female lead, and then they choose the main female lead... interested in 3rd girl and best friend to males love interest, names elude me.
Nyan Koi, same reason as Nisekoi. The turned Kogal, the bi-shounen trap (fanbase don't seem to like her much), and the stalker twin.
Would love to see more to Karin in this way.
Seitokai no Ichizon well suited to a dating sim format.
I might actually enjoy Hayate no Gotoku!! again, if it was a VN.