I think there are pros and cons with each Sims games.
Sims 2: The focus became with the idea of raising a family and having a sold income. There was more of a background story with the pre made Sims and they felt realistic. The towns, houses and custom content reflected 2004-2008 I would say. Sure the graphics aren't up to scratch with Sims 3 and Sims 4 but that never mattered. The game felt like it could entertain you for hours and it still can. It's expansion packs are delightful and entertaining and nothing could ever take it's place. Plus for a game from 2004, it is still amazing. I preferred building in the Sims 2 because it was easy and not over complicated. Plus you could build realistic houses and they felt like homes.
Sims 3: Here, Maxis listened to us and expanded the Sims to celebrity stardom and focused on fantasy. We got excellent EP's like Showtime and Generations but they really stood out. The graphics looked a lot more realistic and the open world really changed the game. I felt like Sims 3 could never have worked without EP's than Sims 2 because the EP's made the game work. Sims 3 was more better for story telling in as Generations allowed more than just your basic family stories. I do think Sims 3 was a lot more fun, there is more opportunities to go and do activities and being a superstar is every person's dream. Whilst building was sometimes difficult, it was enjoyable and easier. I think with Sims 3, some houses didn't feel like homes, maybe through the way I designed them or because the focus was more on having fun and having a standalone superstar Sim?
Sims 4: The newcomer to the game, although two years old. At first I didn't like the Sims 4 at all. I remember getting it and thinking how claustrophobic it felt. The open world was gone, sure we could walk a few yards outside the house but it felt like it was pointless. The transition from baby to child missed the toddler stage, the kids grow up too quickly and it feels as if Maxis has no idea what they wanted the Sims 4 to be. I know they scrimped on the graphics in favour of low memory but it really changed what Sims used to be. Arguably, I get why they changed the Sims 4 from the rest. I can't comment on the expansion packs that much but for what is already out there, they are quite poor. I feel as if the money charged doesn't justify the content given. Plus cars were a bonus in the Sims 2/3 and loading screens whenever a Sim goes out can be tiresome when looking at the screen. All it feels like is having a job and not doing anything, even raising a family is a bore. Lack of lots is also a problem, It is really annoying having to build and remove a lot (which in itself can be difficult)