Anyone who has played the previous Sims games will feel right at home with Sims 4. I have played a family for over 10 hours now and I find myself enjoying the game.
Sims 4 improves on some problems and limitations that existed within the past games. For example multitasking has greatly improved the games realism. It is now possible to eat and drink at the same time. It is now possible to drink while going to the bathroom lol. It is now possible to chat with a friend while painting art. There are many other tasks that can be paired but I am not going to list them all and probably I have yet to discover most of them.
Sims 4 also improved on appliances, for example they break less or more realistically. Instead of the toilet getting backed up constantly it now happens a more believable amount of times. The house building tools are also much better, roofs are easier to install. I also, personally, find the design and style of the roofs, walls, flooring...etc. more visually appealing and better matching. You also get a large variety of colors to pick between when buying an object.
The new emotional systems in the game are interesting and I have by no means played around with them enough but they seem to effect your Sim's life. If they are out of of control then your Sim will have a hard time progressing in their career. Emotions also cause many objects to have different options, like for a painter the playful, confident and sad paintings are only available to paint when your experiencing that emotion.
To address some criticism I have seen regarding the lack of objects, I will say that I am happy with the game's amount of objects. Sure pools may not be present but well this time you get a piano and violin without an expansion. The objects are there but with just a few differences between which ones are offered in the base game.
I only experienced one bug when playing, the super super fast speed, which was not even present in Sims 3, sometimes does not kick-in when it should or at least when one would think. That being said Sims 4 has a super super speed for going to work and sleeping! YAY! So far it seems Sims 4 is more stable than Sims 3 is today, at least for me.
To address new comers to the series, do be careful, Sims is a great series but an expensive one if you want all the content, a lot which was cosmetic in Sims 3. Expect to pay 100-400+ more dollars over the next few years if you want all the content. That being said I love this series and gladly pay it. Considering how many hours I play this game compared to other games it is worth it.
The reason I gave the game only an 8 was because to me an 8 is a GOOD SCORE. My 9s and 10s are reserved for games that deliver entirely new experiences, ground breaking games. Sims 4 is just a much better and refined version of a game that already exists. I hope you will find this information helpful when deciding to make the purchase or not.