I've been playing the Sims since the first one was released, and I'm still playing the second one to this day. The Sims 2 Ultimate Collection that EA released on Origin to celebrate the release of the Sims 4 actually works with no issue on my current computer, which runs Windows 8. I had problems before getting TS2 to work with Windows 8 when I tried to install from my CDs/DVDs, but downloading the Ultimate Collection made the setup really easy, and I could play with very little issues. (The only issue I had was because of how I set up new neighborhoods. Finding the correct files to delete and replace took some time.)
Obviously the Sims 2 is my favorite of the series. When I played the Sims 1, there wasn't a lot to keep my interest, since the Sims couldn't age. Once my Sim married, had a child, and bought every expensive item in Buy Mode to furnish their mansion with plenty of money left over, I became bored with the game. So even though I have the entire Sims 1 collection, I haven't played since 2006, when I got TS2.
And that's my favorite because there's so much to do. With all the expansion packs installed, there's so many activities and other new things to try, even for veteran players. But the best part about the game is seeing how families grow. See which Sim likes which other Sim enough to marry and start a family with (or which Sim works best alone and gets impregnated by aliens!), how their genetics combine, who their children will grow up to be. The legacies just go on and on for however long the player is interested.
What probably helps that for me is all the custom content I downloaded for TS2. I honestly think that the community that built up around TS2 was one of the best I have ever been in, and unfortunately it all ended with the release of TS3. There are still some very stubborn TS2 players around, but the community is nothing like it was. The custom content created for the game, either hacks or items, help to keep the game interesting for me. For extra challenge, I have hacks to keep job earnings low so my families aren't rolling in the money by the time the Generation Two kids are teenagers.
I really just play the game normally. Right now I'm doing a complete custom neighborhood, minus the terrains. (Never got the hang of doing that in Simcity 4!) All the lots are ones that I build myself, all the neighborhood decorating is done by me, and most of the Sims are my own. I divide my time between building and playing one family, which I really just started. The second generation of that family are children, they have no money, but I'm really enjoying my time playing the game again. Sometimes I micro-manage them, but usually I just pick one member of the family to keep an eye on and let the others do their own thing.
As for the Sims 3, I haven't played it at all. There are some features I like the look of, like the open neighborhood and how expanded Build Mode is. On the other hand, I've been watching some playthroughs of the game, and it seems really laggy, needs various hacks just to make the game playable, and I've heard the game is just more boring? Less life-simulation? It's just not a game that feels like a Sims entry.
With the Sims 4, I think one problem is the fact that the game just came out. It's only the base game, so there's no expansion packs to add new features and content creators haven't had a chance to fix some bugs or add their own improvements to the game. There are things in the game that have received praise, like multitasking and the new emotions system. Plus there's some humor in the game reminiscent of Maxis's. Then there are the problems players are having with the game, like bugs or how difficult it is to do even the basic day-to-day tasks in the length of a Sim day. (I've heard it's really difficult to make and maintain friendships, which are still necessary for promotions.) But it's being called in some circles the "actual" sequel to the Sims 2, since it makes some return back to the way that game played compared to TS3. So maybe that's a good sign. Only time will tell, depending on how EA handles the expansion packs and what's released in them.
