My opinion here is complicated for me TS2 has been the best so far even the sims 1 was great. But here it goes. I'm only giving the sims 4 a chance cause I still love my sims and the concept of the game is great and the sims 3 is horrible in my opinion. I haven't played it but I think the sims 4 will satisfy me more than the sims 3 after a few EP and here is why...
The sims 3 are ugly and I'm all about pretty sims hopefuly realistic as well so I would get CC all the time, but the sims in general were ugly. Another thing I hated was the lack of interactions between sims, I mean TS1 Hot Date had so many interactions and TS2 was awesome for story telling I had a lot of fun with it. The bugs in TS3 were ridiculous as well I had to become like a computer engineer to fix some of my problems and trust me it got annoying and then I install a patch and everything went to hell. CASt was also very annoying in my opinion not so much in CAS but in build mode. This is why I don't really support TS3.
I'm giving TS4 a chance because although the sims look extremely cartoony and the hair is just horribly made. However the sims are adorable now and they are very unique and we can finally play around with different cultures which I think is amazing and I look forward to it. I also think EP could give this game a good shot, but I doubt toddlers will ever be back so that has me a bit worried. I don't miss CASt so much except in CAS but I'm glad build mode will be more simple cause the sims 3 was like a game for architects and indoor designers and at least the way I play I like to create a sim and just play with it and decorate rooms but I hate building houses so I just download pretty places and decorate them.
These are the reasons why I'm getting the sims 4 and think it will be better than the sims 3 with time... (hopefuly)