If you are looking for good writing, and worldbuilding then I would recommend:
- Muv-Luv Series (Muv-Luv which contains Extra and Unlimited, Muv-Luv Alternative, Muv-Luv Total Eclipse, Muv-Luv Phontonflowers, Muv-Luv Phontonmelodies, Muv-Luv The Day After)
- When They Cry (Higurashi, Umineko, Ciconia)
- Dies Irae
- Muramasa (Warning as it is quite dark)
- Fate Series (Fate/Stay Night, Unlimited Blade Works Movie, Fate/zero)
- SciADV (Chaos;Head NoAH, Steins;Gate, Robotics;Notes Elite, Steins;Gates 0, Robotics;Notes DaSH, Chaos;Child, Occultic;Nine, Anonymous;Code)
- Baldr Sky
- Rewrite as mentioned above
- Infinity series (7/17/11/12 as Never7, Ever17, Remember11, 12Riven)
- Tsukihime
- Dangnaronpa series (Fun)
- Utawarerumono series (Prelude to the Fallen, Mask of Deception, Mas of Truth, Monochrome Mobius)
- Grisaia Trilogy
- Majikoi series
- Fata Morgana Series
Now, from this side of the world, I would recommend:
- Mad World
- Out of Touch
- Monster Girls Quest
- Divine Dawn
- Companion of Darkness is really green but shaping nicely