As someone who has played all all four iterations of the Sims, TS4 has held my attention the longest as it has allowed me the most flexibility to tell my own stories. I remember liking 1 and 2 well enough (haven't played them in years now), but I remember preferring other games at the time and only playing sims once in awhile (partially because of the loading time). I played 3 pretty heavily for about three years and had a good time, but I had to mod it up pretty good to make it run properly, and those mods ended up slowing the game down so much as to make it unplayable for me. Once I tried 4 (after the release of toddlers and vampires) I never went back, as it ticked most of my own boxes for what I wanted in a simulation game.
Like others have said better than I can, each version of the game has its own style, and what works well for one may not be to another's liking. Doesn't make one objectively better than another. For example, there are things in 4 that none of the other games ever had, but that doesn't retroactively make the older games incomplete of lacking in value.
