The things I like about the Sims 4 are the following:
Art style: The art reminds me of an updated Sims 2, which I really like. I also enjoy that it isn't too cartoony, but not super realistic
CAS: I like how we can go into a lot of detail to create a sim, and make them fully how we want them to look. Base game has quite a bit of good clothes and hairstyles.
Pets: I miss horses fro Sims 3, and that pets could have careers in the Sims 2, and that my first pet stuff was not with the expansion, I love the Sims 4 pets. I like how you can use the paint tool to create exactly as you want now. I have downloaded pets from the Gallery, and have had really cute pets. Some coat patterns carried over completely in the offspring, while others got the basic version of it. I could go on about the pets, but I can do the same for the CAS for the regular Sims too.
Worlds: I wish some worlds had more lots, but with the worlds I have, I do enjoy them. i am just missing Cottage living with the world type packs, but from what I have it is pretty decent. i converted some lots into stores, and other places, so I really enjoy what you can do with them.