I really like seeing how everyone supports TS2 and the comparison to TS4 - I often feel as though I may be the only one who feels the same, but I'm glad that I'm not.
I actually tried playing TS3 yesterday because I wondered how I would compare base games, right here, right now. I didn't like TS3 very much. I did enjoy the amount of stuff that was in the game, but at the same time, it felt clumsy and I was ultimately bored of the open world after 30-40 minutes. However, I did end up revisiting Ambitions, and I learned that I enjoyed Ambitions a lot more than I did a few years ago when it was released. Oddly enough, I also found TS3 to be a lot more boring and clunky than I remembered.
TS2, for me, has always had a solid base game. I did play the TS2 base game quite a bit, but I must admit, TS4 has a lot more stuff to do. The interaction between Sims in TS4 is far more advanced, and makes a lot of interactions more easier and fun to do. I definitely think that TS4 has a solid foundation of social interaction in the game with other Sims, but they need to open it up a lot more. I want to do group/trio/duo interactions more often that are fun to do and are different. I would really like to see fancy restaurants, cafes, etc. I think that they could create a layout for shops and stuff, and then just reuse that same layout for different venues. They could recycle some animations/functions, but with different routing paths and/or objects, if applicable.
One thing I like about TS2, though, is how great the lifestages are. Like I said, TS4 has that foundation of great social play, but it is really only amongst teens/young adults/adults. Children are a lot of fun to play, and I do like the interactions you can do with the baby. I did get used to the baby being in a bassinet after playing TS2. It's cool that you could walk around with your baby and stuff, but I noticed that my Sims would often put the baby on the floor and it would just sit there. I then realised that I preferred TS4. However, I like that TS2 had lifestages that felt like they meant something. In TS4, it doesn't really feel like the baby lifestage "matters" that much. That's why I would really like to see toddlers ... toddlers, to me, felt like the bridge between baby and child. Even though child has always been in the game, I actually prefer playing the toddler because it is so different, and in between the baby/child. I always liked TS2 for how they approached family play, and I wish that TS4 had more of that approach.
Ultimately, I have to say that I enjoy TS4 a lot more in terms of base games. TS2, to me, did feel "secluded/isolated". I play TS4 and see the backdrops and everything ... I really enjoy them, and it makes the game feel alive to an extent. I also really like having the "goals" in TS4 for social events and whatnot. I do think that they need to last longer, because the social events don't really feel "established" in the allotted time that they give. I would like to see an option to have "extended" hours, where they go on for double or triple the amount of time. It would be slightly harder to level up, but not by much. I also think that you should be able to turn off the goals so that people can play a more sandbox-y game. I would also really like to see toddlers back in the game to give more weight to the earlier lifestages.