I don't really have a favourite developer despite having read 100+ VNs. Used to like minori (for ef) until I tried one of their more recent games (sex, boobs, sex, did I mention boobs?). Used to like Key until my tastes changed (still love Rewrite though). I can't really judge a developer (assuming they even have some sort of a policy in place and don't leave everything to the writer) without having played a good amount of their major titles and I'm still somewhat new to the world of untranslated VNs, but I do have some candidates:
- Moonstone. For Princess Evangile and Natsu no Iro no Nostalgia. While I didn't enjoy these games all that much (prefer plot titles over moege), I liked the writing, especially the way Kure makes protagonists. Will be more sure about these guys once I read Doko e Iku no, Ano Hi and the upcoming big title.
- SORAHANE. For Haruka Kanata alone. It's a game that left a very long-lasting impression on me and I'm excited for whatever it is that's coming up. I also played their first game, Aqua, it had its good points but I didn't really like it for a bunch of reasons.
- Makura. Because of H2O -Footprints in the sand-. The plot is different from the anime, there is less of it, but having looked at the anime synopsis I can say I prefer the VN version. The fandisk/side story as well as Supreme Candy disappointed me greatly, nonetheless I definitely want to play Himanatsu and Sakuuta before I make my judgement on this developer.
- Lump of Sugar. Reeeeeally not sure about this one. There's things I like and things I hate here. I loved two routes in Hello, good-bye as well as Uzuki route in Gaku Ou (though the rest of the game is utter boredom). Placing all of my bets on the big one. There could be a surprise coming with Tayutama 2 since apparently the writer is a new guy no one knows anything about, but I'm not holding my breath.
- Nanawind. Again, a good impression from their first game, Yuyukana, even if it was mostly the same plot in every route. Loved the art style, liked the music and the absence of loli. I'll have to play Alia's Carnival to know for sure.