My metric for AVNs is not even all that complex, not on the level even of as deep as what your saying your friend used to do.... just simple depravity rules.
Hot women never die, are always seduceable, and should always have many scenes with each woman, that are high frame, multiphase, explicit in the extreme, well blocked, and angled, well lit, with a great control UI, and touch on as many taboos as possible, without changing the gorgeousness of woman in any way (so no weight gain, or pregnancy :P ). Aside from, no hard lockouts, or dead-end gameplay... even if it means you have to give the most unrealistic immature or even slightly sociopathic reasons for why all the Romance paths in the game were capable of being salvaged in to Harem ones.
In other words, the sex, and the ego masturbation for the PC, is all that needs be top shelf. For that? I am happy to sacrifice any realism, entertain the most hilariously tenuous logic, crazy story, unrealistic everything and anything, and mediocre narrative.
I am simple man, who needs but simple things.
Of course, if the story IS good, the ambience of the game on point, with great graphics, lighting, pacing, immersion, with perhaps even real top tier trimmings like quality voice acting, well even better.... but NO ONE has made a game like that yet, not even the BEST rated ones in the genre on here and steam..
So as long every hot woman is a Harem option, and by the time the game ends we've had the option for copious amounts of depraved taboo sex with them, in high quality, long, well done scenes, and there is NOTHING that gets in the way of that, even if SOME women were meant to be monogamous Romance pathways, then I am happy.
Just hurts my depraved perverted soul, to see women who are definitely worthy of my PC's terrible sex game, only get it fleetingly, in one of encounters... or not at all. It is spiritually painful :P :P