I like the graphics more in 3, theres more detail in the textures and there's far more small details to find or add to your lots.. the sort of details you only get in a PC game. Sims 4, everything is larger, more clear, but ultimately less detailed. I think those graphics could work on a mobile device and fit nicely. Sims 3, details would just be too small. Think about the UI for instance. Ive taken some comparison screenshots.
Sims 1
http://i.imgur.com/UN1dCtD.jpg
Sims 2
http://i.imgur.com/gPvxtst.jpg
Sims 3
http://i.imgur.com/IyVFYdj.jpg
Sims 4
http://i.imgur.com/iJYL6LR.jpg
To me, Sims 4 is the furthest from the norm. Call me judemental but I think Sims 4's UI looks designed for a touch screen device, like an Ipad or similar tool. It doesnt contain the pin-point accuracy and detail a mouse and keyboard can take advantage of. They have removed it's complexity.
Same with the graphics. Here are 2 of my builds, from both Sims 3 and 4. The biggest different I see is detail. We are looking at the exact same thing, yet one looks less detailed.
http://i.imgur.com/TqP39kf.jpg
Sure, on it's own Sims 4 looks nice. But really it doesn't offer me much in terms of pin-point complexities.
So to sum up my opinion, It would be that Sims 4 is a step backwards in terms of PC interface and graphics. It's slimmed down, and simplified. A common argument is to save on performance, but really, with the amount of computer power available these days it's shooting yourself in the foot to play it so safe and not advance with the times. I wish Sims 4 would push the boundaries of what's possible in a life sim, not take a step backwards from Sims 3's open world and graphics. Sure, Sims 3 wasn't perfect, but it could have just been a stepping stone, or a baseline for a new formula. Why not build on Sims 3 weaknesses, instead of skipping it's progress completely?
Also, graphics and UI aside, Sims 4 comes up very short when it comes to family play.