I love The Sims more than I love the RCT series; and that's saying something.
The Sims was absolutely amazing when it first came out, the thought of controlling someone's life to your heart's content made me extremely excited. Also watching my older sisters play it made me even more excited but I just didnt understand the game at the young age I was when my sisters had it. Once I was old enough it took a long time for my impatient sisters to teach me the basic instructions of the game. I was hopeless at first, but after a while I started to get into it and would play hours on end. Another thing I loved was that it was not TOO real. There was a cartoonish feel to the characters and the things they did which I love!
The Sims 2 was a massive step forward for the franchise, the change that got me the most was the Sim customisation which I find absolutely amazing. Also, the graphics of the game was a huge improvement from the first game.
Then there is The Sims 3. Before it came out, I was expecting more of a change, more objects, a huge variety of jobs. And I'm not sure why, but I thought it would've been great if you could actually go with your sim into school or work and interact with colleagues or teachers etc. but what we got was just about the same thing as The Sims 2. The only difference was you needed a super computer from the future to run the game smoothly without lag. But nevertheless I still play on it hours on end (mostly trying to ignore the lag it has on my computer...)
Now, I really hope the Sims 4 is another huge step forward like the sims 2 did to the sims 1. I would also like more customisable building items (curved walls, ceiling windows etc.) to make the more modern house. I think it would also be awesome to have some tribute items from the first Sims to really bring back that charm that the Sims 1 had.