Bunnies. No sims game before now has ever had bunnies, and they are adorable. More interactions with farm livestock, so it seems more like living on a farm. And llamas, of course. We never had them before, either. One reason I finally decided to buy Sims 4 was because of Cottage Living, and it has not disappointed. I love the world, I love the small town feeling, I love the added game play. An outstanding pack.
The out-of-the-box sims in Sims 4 are potentially much more attractive, with more detailed clothing and hair. I do not feel the need for CC skin, eyes, hair etc. It took me a while to figure out how to manipulate CAS, but after numerous redos of townies and new CAS sims, I have it figured out enough to get the look I want. It took me much longer to master CAS in previous sim games. And because I bought the game late in development, CAS has a plethora of clothing/hair styles. More than enough to make every sim unique.
But the real strength of Sims 4 is building. Truly amazing what can be achieved, with very little effort. The ability to move houses on the lot after they have been built, to move individual rooms, to change the height of walls, to change foundation heights at any time, to place windows and doors incrementally instead of just to grid, to size objects up and down, to make a transparent roof - it is a builder's dream! I have never enjoyed building as much as I do in this game.
Another reason I decided to try Sims 4 at this late date was the truly excellent UI type mods that allow me to play Sims 4 almost the same way I played Sims 3, and the fact that the mods are more "supported" than they were in Sims 3 is a bonus. Also I like the truly excellent smaller mods that tweak game play to remove annoyances, and how nicely they play with the bigger mods. Sims 4 is a more stable game, especially concerning how it interacts with mods, and I greatly appreciate that stability.
I really like that I can delete townies and NPCs or easily replace them through CAS, seemingly without any negative ramifications. Trying to do that was a game breaker halfway through Sims 3, and I did not enjoy having to live in almost unchanged EA Sims 3 worlds. So the ability to adjust the sims in my many Sims 4 worlds is a welcome freedom.
Sims 4 is less of a strain on my eyes. I notice when I switch games that I can play longer without discomfort in Sims 4 compared to Sims 3. Reduced eye strain is always beneficial.
I am very happy that I can play Sims 4 on my Mac, without it being worse game play than on a PC. Sims 3 plays best on my old PC, no question - it never did play well on a Mac. I did not want to get a new PC that might not play Sims 3 as well as on my old one, just to be able to play Sims 4. Knowing that I could easily play Sims 4 on my 2020 iMac was a deciding factor in purchasing Sims 4. I sincerely hope EA fully supports the new non-Intel iMacs and all new Mac OS as well. I want to play Sims 4 on my Mac for years to come.
I like that Sims 4 has been more responsive to fixing bugs. Oh, I know that some things have not been fixed for a very long time. But in Sims 3 we had hardly ANY bugs fixed, and the game became more and more unstable because of it, with some major features completely broken in later expansions. I am glad to see that Sims 4 is still stable and relatively bug free in comparison, considering the game's age and number of add-ons.
I really like that EA recently made more wood tone swatches for older objects. I hope that trend continues. If we had the same wood tone swatches through all the different objects, then I would not miss the color wheel from Sims 3 nearly so much. I just want matching wood tones throughout each house, and the more swatches I have that match, the more items I can use in any given build. (For instance, I would LOVE the rocking chairs to have matching wood swatches. I use them in every build, and it would help so much to have them match the other furniture.)
And I agree, as others have said, that the best part of any sims game, Sims 4 included, is the Sandbox. Never take the Sandbox away. And never take away our ability to play offline whenever and however we choose. As far as I am concerned, those two things ARE the franchise.