Sims 2 Game Play
-Memories
-Interests
-Attraction and rivals who are also competing for the sim your sim likes
-Fears
-Aspiration failure (maybe not as cartoonish as TS2)
-Cause and effect (your enemies will come at you, romantic betrayals are dramatic (and not fleeting), hostile sims need a cool off period, unless they are evil or hot-headed, )
-Slightly more adult humor and situations
Sims 3 creative tools and world
-Open world
-Create-A-Style
-Lot placement
-Create-A-World
-Objects with more detailed meshes and textures
-Sims 2/3 Younger looking teens, or TS4 older teens with younger teen stage added.
Sims 4 Sims and miscellaneous features
-TS4 styled sims with more detailed meshes
-Hats on any hairstyle
-Saving and placing rooms
-New Build mode features
-Buy/Build search feature
-Etc. There are a lot of nice TS4 features I would like to see in the next game.
If we can't have a TS3 type open world, but get another version of TS4's world, each neighborhood will have to be big enough to hold nearly every community lot type. Basically, a TS3 sized world divided up into districts, and each district does not need loading screens for lots within the district. You go outside the district, you get a loading screen. Heck, I would even settle for half the size of a TS3 world--Say 50 lots in all, about 10 lots per district.
And the sims waking around the neighborhood should be a majority of people who live there.
The sims 4 feels odd to me because my sims have to travel what feels like a long distance to visit certain community lots. I also don't like seeing so many of my sims taking a jog so far away from home.