I actually play all four of them right now, well not at the same time ofcourse. I play Sims 4 the most now for the past few days since I set up some rules for myself (always repair items (no replacing), always let me sims clean after themselves, not making too much money). Sims 2 I play for family gameplay and the seaons and Sims 3 I play when I want to play with pets. Sims 1 is obvious, sometimes you just want to go back to the good ol' times.
So just split your time and see what you find more amusing. Thing is your likes and dislikes can often shift between games, every game has something I like and dislike, so I started seeing them as seperate games instead of a huge series. Made it easier for me.