Tsundere. Cold on the outside, acts like she hates you, then shows the warmth she has on the inside when she finally feels loved. Black hair, Pale, Blue Eyes. Perfect example is Bella from Sisterly Lust.
I think the first I played was Date Arianne the SFW version. I don't remember where I played it, but it made me want to try the NSFW version so I sought that out. Ever since then I've been into these games
As long as it's not entirely copying from a single other game i don't care about it. Most models and locations that we see in multiple different games are already not unique.
If they're still ongoing games in look at the history of how often it updates, if every update has content, and if it's been dragging stuff out. Besides that I look at tags, models, reviews, and future plans if the dev has layed those out.
It depends on all the girls in the harem. If there's a girl I want nothing to do with, then I find it hard to do the harem if she's included. Also if there's a single LI that's above and beyond the others then I might just want a solo ending with her