The British magazine PCZone has had an interview with Tim LeTourneau, senior producer of The Sims 2. Of course the topic of the interview is The Sims 2, but also the reason of the success of The Sims:

"At Maxis we feel the key reason The Sims is so popular with both male and female gamers is because people can easily identify and relate with the Sims and their environment. Players become sucked into this alternative sand box reality, its gameplay based on the key desires we all have in our every day lives. However in the Sims world things are very quirky and fun, we don't have to live with consequence of our actions, good or bad in quite the same way!"

That's only a (very) small bit of the whole article. If you want to read it completely, click here to see it.