All of these Sims have good genetics in my opinion (that are near YA, YA or Adult)
Emma Hatch and Claire Ursine (after a few hours at the gym and a much needed make over), Agnes Crumplebottom, Morgana Wolff (married), Bebe Hart (3 days from YA), Holly Alto (4 days from YA), Jamie Jolina, Pauline Wan, Zelda Mae and Tori Kimura.
Personality factored in: Emma Hatch, Morgana Wolff, Bebe Hart and Holly Alto are my top choices.
Holly Alto and Morgana Wolff have the added benefit of having more money.
While I wouldn't consider her a knock out, I think she deserves a mention. Every time I've had my sims have kids with Ayesha Ansari, they've been good-looking and she has a good personality though she works in the criminal career.