In The Sims 2, I would always go for either Don Lathorio and see how far I can get his relationships with all of his 'women' ;) Either that, or I'd play the Pleasants and see how far I can get the dad into cheating on his wife with the maid (one time he got her pregnant and left his wife for her, oops.)
In The Sims 3, I opted for the goths at this time, although I loved them in the sims 2, I love making their story begin by making Bella realize that she wants to befriend Mortimer no matter how weird everyone else things he is, and then they fall in love, and well, you know the rest, haha. I also enjoyed the Keatons, I don't know why but I loved the idea that EA put in a pre-made pregnant sim. I've also messed around with Christopher Steel, he's gotten married to that one townie who's in the military, and she's got like that green dress on, can't think of her name at the moment, lol.
In The Sims 4, I don't really play with any townies. I usually create my own and then have them date some of the townies, like Johnny Zest. I've made Eliza and Bob have a baby once, that was the last time I played them though. Although, I love the new aspect EA added in with the Hecking family in Cats & Dogs :) <3