Yes it's the same creator behind the game and the video so it's kind of like a remake? or at least it's very inspired by the Eri route he made in the game. Well like you said in the game Eri is the classic nice and caring mom archetype but deep inside she is sexually frustrated. Yamato opened her eyes to the real sexual pleasure, she became a woman for the first time of her life thanks to his magic cock lol. And she became so addicted to sex with him without any blackmail, drugs or hypnosis it's pretty funny.
It's quite hard to make a top 5 but if i limit myself to only eroge (no rpgmaker/doujin games) and only real "mom" with a child and no "older women" type of character then i guess it would go like that :