I was a huge fan of The Sims - and when I first saw The Sims 2, I thought the same of that as I do now for The Sims 3. I was quite happy playing with my family - always the same one, can't actually remember the name but I had my Superstar (I created him and progressed up the ladder myself - no marrying other Superstars!), with his wife (Celebrity, I believe), and their child. The Sims 2 held no interest for me until around the time that I bought the preview disc.
However, after playing around on Bodyshop, I was totally hooked.

I made whole families on there, fascinated by all of the different age groups and options available. I bought The Sims 2 on release date - it was a little confusing at first (especially as I skipped the tutorials

It took me months to work out how to place a roof!) - but I got the hang of it. Haven't looked back since. I definitely prefer it to The Sims, although, I do enjoy playing the original game now and again.
I was quite excited about The Sims 3, but now I just don't see the appeal. I hate the way that everything looks. It's so plastic and.. fake.

I don't plan on buying it on release date, but if a preview disc is available (with a The Sims 3 version of Bodyshop, perhaps) I'll buy it without a second thought. I'm not quite sure I'm ready to stop playing The Sims 2 yet, after getting so hooked to my Legacy family, but who knows.

In short - not particularly excited about The Sims 3, but in my experience, this can change pretty quickly.