Without. Even if I don't self insert, I still have a preconceived notion of what the MC looks like and it never aligns with what the dev picks which screws with my head cannon for some reason.
Such a Sharp Pain (SSP) and Everything Gets Boring Eventually (EGBE). Unfortunately the author (Ketzal) had his accounts nuked, so the future of these games are in doubt.
Story. Sex without a good back story is boring. In fact some of my favorite stories are "slow burn" where it may take a few chapters to set everything up before sexy times even happen.
I agree the dick that is the size of the MC's forearm that he proceeds to stuff in every hole the LI has with no prep of any kind is a turn off.
The biggest issue for me though is bad dialog. Top of the list is bad translations. If the grammar is bad and the word choice or context doesn't make...