Muv-Luv series
- Generally considered one of the best VN series around, mainly for Alternative, but Extra and Unlimited are pre-requisites. Revolves around a post-apoclayptic world where humans have been pushed to the brink of extinction due to a alien species known as BETA (Beings of Extra-Terrestrial origin and Adversary of the human race). Humans have developed Tactical Surface Fighters (TSF) which are basically giant robots which are the only weapon effective against the BETA. The series revolves around a guy named Takeru who is somehow able to cross worlds and his attempt to save the human race. This is the most understated explanation of the game, but if you read any reviews, this VN series is almost universally praised.
Aokana - Four Rhythms Across The Blue
- A world where humans discovered an anti-gravity particle that allows them to fly. They develop a game/sport called Flying Circus (FC) where they fly around to touch buoys to score points. The story revolves around a guy who was once an up-and-coming star in FC, but gave up his dreams for some reason. Considered one of the best character-driven game of all time and one of Sprite's best works. There's an all-age version available.
Planetarian
- Short (About 5-10 hours) story about a human and an female android in a post-apocalyptic world. It is considered one of Key's better works and is all-ages.
*eden
- Short (5-10 hours) story about humanity's decision to leave Earth due to a comet which would hit Earth in a couple of years. Resolves around a hyper-intelligent bio-engineered girl who decides to remain on this planet and the guy who decides to stay with her until the end. Base version is all-ages.
Sharin no Kuni, Himawari no Shoujo, and its sequel, Yuukyuu no Shounenshoujo
- Revolves around a group of elites called Special High-Class Individual who are tasked with re-educating and reforming criminals. The main character is on his final exam to be a Special High-Class Individual and his final test is to reform 4 girls. One of the best character-driven VNs ever.
G-senjou no Maou
- Revolves around the brain of a yakuza enterprise, an extremely intelligent girl and a mysterious hyper-intelligent criminal called Maou. A cat and mouse game between the girl and Maou ensues. If you like wit battles, this game will be a god-send.