Honestly the writing quality really surprised me. The sex scenes I was expecting quality going from the writer lineup, but effort has been put into areas I never really thought about in CoC1 or TiTS that make the whole thing more fun and cohesive. All the effort to have companions remark on events or each other, questlines that relate to each other in ways you didn't expect, actual twists in the story I'd feel bad for mentioning. Hell, while there were characters I definitely cared about and enjoyed in the other games, I'm usually enjoying each character even if I'm not interested in their sex content here. Felt dumb for writing off Cait at first for instance, her dialogue and interactions with others are some of the funnest bits of content in the game.
I've also really gotta commend the combat system. People have talked about the quality of the build-making and overall flow to it, but the fact it's so ambitious and yet is so easily readable and comprehensible is insane. I was kinda worried back when CoC2 was first coming out it'd get too messy, but even in its much-more-complicated form now it's still something I enjoy interacting with and theorising builds for (did not expect I'd be staring at stat screens and wiki equipment entries for a game like this, but they did it).
Also, Kasyrra. Absolute triumph of a rival character for reasons everyone already knows, both in terms of being a really fun over-the-top villain, and that kinda-twisted-yet-earnest romance that seems to be able to develop.
Also everyone's pretty hot.