I've been doing a lot of research into visual novels lately, primarily to chase down the additional Da Capo content I didn't feel I was getting from the anime series. But the truth is, beyond Key and Circus, there's a great deal of other famous, good visual novels as well. Generally the best ones are adapted into anime (whether the adaption is good or not is another question), and many of those anime series feature in my rankings -->
5. Mahou Shoujo Lyrical Nanoha (First featured in the visual novel Triangle Hearts)
11. Higurashi/Umineko no naku koro ni
13. Da Capo
18. Angel Beats (a Key written anime script, which is getting a visual novel prequel)
32. Galaxy Angel
43. Little Busters
76. Amagami SS
84. To Heart
89. Akaneiro ni Somaru Saka
118. School Days
126. Tears to Tiara
So out of the top 130 anime series, 18 of them were inspired by visual novels, many of these top ranking works. Eighteen isn't an overwhelming number. It's possible to be a good anime series as an original work (like Pretty Cure or Code Geass), a manga, (Like One Piece or Naruto), a light novel (like Haganai or PapaKiki), a film (like Summer Wars or Princess Mononoke), a video game (like Idolm@ster or Valkyria Chronicles), or even a novel (like Shinsekai Yori). But the point remains that there is a lot of gold to be mined from them there hills.
Visual novels were previously constrained by the limits of computer graphics to the point of just not being possible to be good. Without lots of good music, full voice acting, excellent and plentiful drawings (both for character sprites when they were talking or emoting and fixed events that show off important moments in the story), and a long and involved story with many 'routes' (generally girls you can get to know), it simply wasn't really a visual novel. As great as the content from Key's Air and Kanon were, if you go back and look at these games they look like a child's scribbles, nothing like the beautiful Kyoto Animation adaptions that later graced our screens as anime.
Even as we speak, the ever growing capacity of computers is improving visual novels across the board. They are now HD, widescreen, sometimes with continuous computer graphic animation, full voiced, so on and so forth. The production value of visual novels is much better than it was just a few years ago. This was even more the case in the past, where if we have to painfully remember the super nintendo was the expected level of a good graphics game.
To be a memorable game with super nintendo level graphics is pretty difficult. As such, the past is best left dead and buried in the past, game wise. The first exception to this rule, perhaps the date we can label the 'origin' of the visual novel as a true art form that could actually deliver a positive experience, is the extremely famous Sakura Taisen from 1996, published by Sega. Sega would continue to make many more Sakura Taisen titles all the way until 2005. The next important visual novel franchise came out in 1997, published by Leaf, called To Heart. I labeled Leaf as a human accomplishment for their work on To Heart because it set the tone for the industry forever after. Not only was it a great game in and of itself, it was the origin of visual novels as an art form almost singlehandedly. This wasn't the last good work put out by Leaf either. The To Heart franchise continues to this day (via To Heart Dungeon Travelers).
In 1999 Key began its godlike run with Kanon. It took what it learned from To Heart and changed it into a strikingly sad story that would leave an impression on people long after the reader was done.
1999 also featured the Memories Off series by Kid, which has continued all the way to 2009. We likely haven't seen the end of this series. It has a number of ova anime adaptions so anyone curious can look into what it's about.
In 2000 Type/Moon published its first game, Tsukihime. It's the predecessor to the wildly popular Fate/Stay series and has a lot of fans for its own sake as well. Like every other series mentioned so far, it has an anime adaption, but most fans hate it so it's hard to say how good the game is without playing it.
Also in 2000 came Key's next classic, Air. Kyoto Animation strangely picked up this series to animate first, and Kanon second, so many people think of Air as the 'beginning' of what made visual novels great.
2000 also saw the beginning of the Canvas series by F&C. This series also has an anime adaption for the curious of mind. The Canvas series continues to this day.
In 2001 Suika officially began Circus' rise to greatness. It also has an anime adaption, but this is just a portent of things to come. Suika is an avant garde, artsy work that has all sorts of strange ideas bouncing around. Circus admits learning from Key how to do a genuinely moving and heartfelt story with their next work.
2002 sees the release of Da Capo, Circus's paramount work, and perhaps the most important visual novel of all time. This is because the Da Capo series is so popular and resonates so strongly with fans that endless sequels beyond all number have continued to this day. Furthermore, Da Capo has an enormous anime adaptation which is close to 100 episodes long at this point, and will probably continue to expand into the future. Da Capo will dominate the future of visual noveldom henceforth.
2002 also revealed Higurashi no Naku Kori ni by Ryukishi07. Ryukishi07 also says he took inspiration from Key's works, and eventually goes on to work with Key for Rewrite as a sort of natural evolution. Higurashi is by no means the last important work from Ryukishi07. Higurashi and its sequel Umineko continue to have a tremendous impact and following in both the visual novel and anime world.
2002 also sees the creation of Galaxy Angel, by Broccoli. Galaxy Angel in the visual novels was always meant to be a serious love story, which went all the way to 2009 with sequels, but it will always be best known for its comical anime adaption, which it also produced alongside its visual novel stories. The Galaxy Angel anime is enormous and hilarious, so Broccoli did a good job either way.
2002 also sees the return of Leaf with the visual novel/rpg hybrid Utawarerumono. This was the first good hybrid of its kind, so we see Leaf breaking ground yet again. Utawarerumono received an excellent anime adaption that covers the story from beginning to end. Utawarerumono 2 is coming out in the near future. Another Leaf hybrid visual novel/rpg, Tears to Tiara, likewise had success, likewise had an anime adaption, and likewise will be receiving a sequel visual novel soon.
2003 features the beginning of the famous Muv-Luv series by Age. Recently Muv-Luv Alternative Total Eclipse got an anime adaption, but that was never considered the best part of the series. As a result, Muv-Luv may be the most neglected good visual novel series in terms of anime adaptions of them all. Muv-Luv continues as a series to this day.
2004 had a plenitude of heavy hitters, starting with the action packed Fate/stay night by Type/Moon. This was another tradition breaker from what normally are simple romance stories in the rest of the genre. Fate/Stay as a visual novel has had a series of sequels spanning to this day, but strangely its anime adaptions have ignored them all and focused on spinoffs instead. Even the original Fate/stay night storyline was never fully adapted by an anime.
2004 also had Clannad, Key's seminal work and perhaps the closest work of art to perfection ever made. It was adapted brilliantly by Kyoto Animation into the 2nd best anime of all time.
2004 also had Shuffle, Navel's breakout work, which skillfilly melded a lot of fantasy elements into the routine romance story world. Shuffle has a much maligned anime adaptation, and continues as a visual novel series at least up until 2011. (Surely they'll announce another sequel eventually.)
In 2005 August emerged as a strong visual novel company with Yoake Mae yori Ruri Iro na. It later received an anime adaption so anyone curious can check it out.
2005 also saw the emergence of a great new company, Windmill, with their work 'Happiness.' Happiness also received an anime adaption so it's easy enough to check out.
2005 also saw the entry of Overlook's School Days. This visual novel is historical for its radically bad ending and its atrociously evil protagonist lead. This is the anti-romance of all anti-romance stories, and in this way emerges as a particularly great story alongside the rest of the canon. School Days continues to have a series of sequels to this day, but none as notorious as its original. School Days has an excellent anime adaptation, which was so gruesome most Japanese broadcasters refused to air the final episode, replacing it with a 'nice boat.'
2006 features Ef, by Minori. Ef tells a series of improbable love stories normal romances could never hope to match. The game has an excellent and uniquely beautifully drawn anime adaption, but the visual novels actually went on to produce more content that was sadly never covered.
2007 features Little Busters by Key. Another school romance story that has comedy and tragedy interwoven, and again overwhelming all the visual novel competition. The anime adaption is half done and half in production as we speak.
2007 also has the first work of Minato Soft, Kimi ga Aruji de Shitsuji ga Ore de. This is the beginning of a successful series which includes Maji de Watashi ni Koi Shinasai and all of its sequels which continues to this day. Aruji de Shitsuji has an anime adaption under the English name 'They Are My Noble Masters.' Majikoi has a recent anime adaption as well.
2007 also features the gorgeous Akaneiro ni Somaru Saka by Feng, which has an anime release.
2007 also begins the story of Koihime Musou by Baseson, a retelling of Romance of the Three Kingdoms where all the characters are cute, datable girls. This tale continues at least until 2012, and has an anime adaptation.
Luckily for me, the remaining history of visual novel classics is covered by the invaluable website resource, http://omochikaeri.wordpress.com
Starting with 2008, omochikaeri's heroic bloggers discuss every visual novel coming out in Japan, every month, all the way until the present day. This heroic blog may be the West's only lifeline to the visual novel medium, and I shudder to think of how we'll learn about visual novels any longer if it is cut. From 2008 on, by having a real detailed view of every game that's come out in Japan, I can decide for myself if a game is good or not, without having to consult 'buzz,' 'sales,' or 'did it receive an anime that got buzz or sales?' Fortunately for us, all the best visual novel series listed above have gotten anime adaptions, but unfortunately, many of them have been too short, too inaccurate, or otherwise unacceptable. But at the very least they serve as a quick reference for people who wish to delve back into the past and benefit from the best of the visual novels of the past.
Starting from 2008 on, with Omochikaeri as my guide, my next visual novel post will be about the ones I particularly think promising, which might stray from what sold well or is critically acclaimed like the list up till now has been.