The Sims 1: Life-simulation game! It simulates life! Place a bunch of toilets on the property and watch your Sims come to life!
The Sims 2: Family trees! Family lineages! Genetics!!! Wants, Fears and Aspirations! You live, you die! In between, you do what you want in life!
The Sims 3: Open world! Minimal loading screens! Create-A-Style! Zoom in and mess with the Sims and see what happens on a society level! Customize everything!!! Butterfly pattern on the mailbox, that's doable!
The Sims 4: Emotions! Multi-tasking! Smarter Sims, Weirder Stories. Diverse Characters. Create yourself or someone that you know. Intuitive Build Mode.