I love both Sims and Animal Crossing, but I dont think the games can be easily compared with each other.
Sims lets you handle a bunch of families at once, it gives you a lot more control over buildings, landscapes, furniture and just how the entire place looks like. But it also feels really impersonal, the relationships between the characters around the game are mostly just simple commands and gibberish. The feeling you get from the game is "I am the god of this land! I control the destiny of every single one of you mortals! Everything you see around you was created under MY command! ahAHHAHHAHAHHA!!!!"
Meanwhile, Animal Crossing has a lot more limitations when it comes to managing the enviroment, you only control 4 humnas and building up your houses takes a huge while, and each one is very limited in terms of options. Even trying to decorate your town has a lot of limitations! ( Where trees and bushes can grow, where PWPs can be put at.) But of course, that means a lot of attention is put into every single little detail of the game, making villagers and NPCs get friendly with you feels really rewarding and all the limitations give you a better sense of acomplishment once you finish up getting all the furtinure for a room or getting that one rare hybrid that just wouldnt bloom or having a villager suggest that one specific PWP you really wanted! The feeling you get from the game is "I am the mayor of this town. I run this place to a certain extent but it all has a life of its own, I am part of this comunity and I must help make it grow. Yeeaaah!".
I have never played a Harvest Moon game, though, and Im not really interested.
I do have to say Ive enjoyed and put a lot more hours into ACNL that into any Sims game.