i never played 1, so i don't have an opinon
sims 2
pros: in depth gameplay, has one of my favorite expansion concepts (bon voyage). i also really enjoy the cut scenes lol. also had the best little details such as hair movement
cons: honestly there's not a con with the actual game content, but rather the fact that no matter what system i play on or the settings, it crashes for me eventually. loading screens are maybe my only other 'con' but i don't mind them much if i'm being honest since there wasn't an open world prior to ts2, so there's no feeling of regression there.
sims 3
pros: this is the first sims game i played so it's my very biased favorite. i love the open world, generations is arguably one of the best packs introduced into the entire franchise, and the expansion packs went really in depth. i play this version of the sims the most to this day, i'll always go back to it
cons: the sims 3 store was a money grab, really laggy at times (especially for the crappy laptops i grew up playing it on!!) and saves always get soooo glitchy after generations of gameplay
sims 4
pros: runs smoothly no matter the system in my experience, and also has the most binge-playable factor. the art style is also probably my favorite if i momentarily stop being so biased towards the sims 3.
cons: the gameplay feels so cold. as a family player, the relationships in the sims 4 feel so icy and meaningless. a sim could be talking to their mother or a homeless man at the park and it wouldn't make a difference. also the amount of loading screens gets old, and the game in general can be really buggy.