If you are only interested in VNs with no sexual content:
-Higurashi no Naku Koro ni, especially with the PS2 graphics and music patches. It's mystery-horror with a dash of comic relief, lots of great characters and a very extensive and complex story.
-Umineko no Naku Koro ni, especially with the PS3 graphics and voice patches. It's from Ryukishi07, the same writer who made Higurashi, and it is a huge-ass story riffing on detective-novel tropes and the mystery genre in general with a great cast and a unique meta-reading approach.
(these two alone should keep you occupied for weeks if not months, depending on your reading speed)
-Clannad, though the translation never got through proper QC before the team disbanded, so it can be pretty rough at times. It's a romantic comedy with spots of drama (a nakige, as the boys in the hood call it), with great humor, generally good routes (save for a few exceptions) an an absolutely great true ending. Be aware that it is extremely long and almost impossible to complete without a walkthrough (unless you want to spend another 10 hours with trial and error, that is...)
-Little Busters. It is made by the same studio as Clannad, and it is the same brand of school life romantic comedy as the former. It also has a very strong focus on a group of friends, friendship, silly minigames and a multiple route mystery with one true end.
-Steins;Gate, as already recommended. Time-travel sci-fi with good cast, 'unique' art and good story. The middle parts are pretty meh, but the beginning and the end are awesome. Get the fan TL and don't wait for the JAST release, it can take anywhere from a few months to a few years for them to actually bring it out even though it is already 100% translated. They have a habit of that.
-True Remembrance. It's a short and well-written doujin game with a good cast and thought-provoking plot. It's about people with the ability to erase other people's memories who work as a sort psychological helpers to help people who want to get rid of certain memories.
-Eien no Aselia. A VN/SRPG hybrid. The story is really, really good, with a good amount of character development and an interesting take on the "boy-falls-into-magical-world-and-has-to-save-it" trope, though it has sub-par art in places and the gameplay is a pain after a while. Using a trainer to bypass most of the grind and stupid restrictions to get back to the actual story is recommended.
If you can actually stomach a few h-scenes (which is not hard, since 95% of non nukige eroges have maybe one h-scene for every 10 hours of reading):
-Tsukihime: It is old and the production values are pretty low, but the story is well worth it. It is an urban fantasy story set in the Nasuverse (in fact, this is the story that introduced the Nasuverse), with a great cast and a logical and meticulously built setting. It has one or two h-scenes per heroine routes, and they are mostly skippable (in fact, skipping is recommended. Nasu cannot write h-scenes at all...)
-Fate/Stay Night: Same setting as Tsukihime, but with an even bigger scope, bigger cast, bigger plot and bigger budget. It's about the Fifth Grail War, a contest between seven magi summoning seven heroes from humanity's legends to fight against each other in a battle royale, where the winner would get their wish fulfilled by the Grail, and the protagonist, a seemingly talentless young mage, accidentally gets entangled into the conflict when he unknowingly summons a Servant when threatened by another. As with Tsukihime, each route has two short vanilla H-scenes at most and they can be safely skipped as they contain little to no actual plot value.
-The Muv-Luv series. The first game is divided into two parts: Extra, which introduces the characters and is actually a school life love comedy, Unlimited, which is an alternate universe with the same characters and it's an after-the-apocalypse world where an alien invasion drove humanity to the edge, and the second game, Muv-Luv Alternative, with is yet another alternate universe with the protagonist remembering the previous one and acting accordingly. The series gets progressively darker as it goes on, and Alternative is actually full of nightmare fuel moments, but it is arguably the best written translated VN out there at the moment. Extra has one H-scenes per heroine, Unlimited is the same, while Alternative is... um... spoilers?
-Maji de Watashi ni Koishinasai. It is a school life comedy set in a World of Badass, in a school filled with martial artists, military guys, ninjas and other assorted goodness. It mainly focuses on friendship, romance and an insane amount of awesome battles and competitions. The normal routes of the VN vary in sexual content. Some of them have none, while others have up to four h-scenes in them. Most of the H-scenes are in the epilogues that you have to open from the main menu. Also, one heroine route and the final route is yet to be translated, but four routes are, and that is about 30-40 hours of reading time right there.
All right, that was from the top of my head. If you would want to search around on your own, hop over to VNDB. Just don't as for recommendations there, we have a policy against that.
