I'm going to start with 4 and work my way back I apologize if I offend anybody.
Sims 4:
Pros - Creating in CAS and building is easier. Being able to change aspirations and start a new one once you're done with the one you are on or you can change your aspiration and not lose progress. Easy to move around from world to world. Graphics are nice. Rotational play is easier to do. Same-sex pregnancies. Teens can live on their own. LBGTQ positive influences in the game. I adore Brent and Brant and just want to go up and hug them when I play. Or Morgyn who I am guessing is supposed to be asexual and intersex. Some of the free stuff is cute and cheesy.
Cons - Playing Vanilla tends to be boring. I feel I need to use mods and CC to have added gameplay. Though some packs are fun and I like them there is a need for improvement with all the occults. Some like the vampires and spellcasters a little less improvement is needed but the mermaids and aliens need a lot of improvement. Please take no offence to this it's not meant to be mean but useless and stupid stuff, game and expansion packs. Do I have to remind any of you of "My first Pet" stuff pack? I think they need to come up with an apology expansion pack just for thinking of that one. The game breaks almost every time Maxis or Origins does an update. Tons of bugs. Traits mean nothing in the game. It tries too hard to be politically correct. Life is never politically correct and EA makes too many "safe" decisions in my opinion. The game as a T, not an E rating. You can do things that are um not for an E rating. No burglars. No consequences for sims actions. For the stuff, game and expansion packs we get very little content. Modders do a better job with their added content (Mermaids, fame etc) than the official release does. Lack of customization I miss the colour wheel for clothing and hair from Sims 3. No spiral stairs or ladders. Too many tiny worlds some of them need more room for us to build. Hats are separated in CAS from hair.
Sims 3:
Pros: You could start as premade sim or create a sim of your own in CAS. the little things. Game, Stuff and expansion packs loaded with content. Sims 3 store. The Gallery, Create a World. (I know some of you didn't like that but I found it fun) Create a pattern. Customization of hair, makeup, skin, eyes etc. through the colour wheel. I loved being able to give my sims ombre hair. I never needed mods to add to my gameplay or for fun CC. Traits meant something. If my teen snuck out after curfew and a cop found them they could be dragged back home. Kids were paid to go to school. More jobs, traits, etc. You could choose your sims favourite colour, music and food and choose their zodiac sign. There were consequences for actions. Being able to own multiple homes and businesses. CAS is pretty to create in. Rich in gameplay and fun can still play nonstop for hours at a time. is pretty to create in. More Occults and Supernaturals.
Cons
Harder to travel between worlds. Forgetting others when you moved to a new world. Graphics, ok but not as nice as Sims 4.
Sims 2:
Pros: I never felt I had to use mods. Interesting gameplay. a little darker at times. Consequences, for your actions. Fears and wants. Memories.
Cons: Some crazy quirks and the game would crash sometimes.
The Sims:
Pros: I think it was innovative at the time. Fun gameplay. Kids were a lot more fun to play in a household. It was fun, different, cute. It definitely made my ex and I laugh a lot. If I was having problems he would take over my game and I would do the same for him.
Cons: Lack of customization. Trying to keep my sim happy and alive through a lifecycle could be really hard. I lost more sims that way.