For me what makes a mom hot in a porn game depends quite largely on the setting and story. The hottest possible mom would be a submissive curvy milf who has her first lesbian experience when becoming her daughter's sex slave. So the criteria, that make a mom hot:
- Be lesbian...: I always prefer mom-daughter games to mom-son games, though I do play the latter, as long as the son is grown man and no teenage virgin.
- ...ideally for the first time: While the daughter should be fully aware of her feeling for women, I like it, when the mom doesn't really know what to do, when her pussy gets wet at the sight of a woman for the first time. Even better, if the daughter realizes (and capitalizes on) the mom's insecurity.
- be submissive: Dominant moms or moms who teach their offspring in the art of sex are not my cup of tea. In the kind of porn games I like, the mom submits the daughter, or, less exciting but still ok, to the son.
- dress sexy: Realistic or not, she best wear short and/or slit skirts and dresses and public and lingerie in the bed room and high heels all the time. The daughter or other women who dominate her can dress more casually.
- biological motherhood matters, social motherhood doesn't: While a mother who gave her offspring up to adoption after birth still counts as a mom for taboo purposes, a step-mom doesn't, especially, if she has no offspring of her own. Step-cest is NOT incest, incest unknown to the characters IS incest.
- don't be too tall. Especially in mom-son games, the mom should be clearly smaller than the MC.
- when the question goes, whether she is a doting mother or a neglecting mother, in most cases, I'd go for the second option, but both are still viable paths. As far as the doting mother goes, I think she works best as a stay-at-home mom and more or less innocent housewife, while a neglecting mom can be some sort of trophy wife.