Hitozuma Koukan Nikki is my favorite Anim game, but Taninbou is definitely my 2nd. Haven't played Boku Mama yet but I'll prioritize it one day. The Taninbou route being so short is such a shame, I hope their upcoming Swapping game can deliver the best of Hitozuma + Taninbou.
My favorite characters would be something like:
1.
Sanae [Orcsoft] [Aisai Nikki]
2.
Aika [NT:Ripper] [Rikai Aru Okusan]
3.
Yukari [Waffle] [Koukan no Toriko-tachi...]
4.
Suzuka [Anim] [Ore no Kanojo wa Taninbou]
5.
Marina [Atelier] [Kashidashi Tsuma, Marina]
All of them share either being netorase games or having at least 1 such route, and being proactive (e.g. Suzuka is Taninbou's eroge engine regardless of route). Their personalities really pop out.
I find it much harder to rate heroines in pure NTR stories since they all feel like walking cookie cutter plot devices. Do I like the character itself, or the story? Hard to say. For example, Gatenkei's Misaki feels too passive despite being gorgeous and having really hot ero scenes, while the opposite spectrum generally feels like cartoon villains. And this is possibly a double-standard.
Characters like Ayaka from
Kenka Saikyou Tsuma or certain RPGMaker heroines would probably be among the top where they are able to obtain a good balance, but I'd have to think hard about it. (And it's not like the amount of games I've played is that large.)