I've never really seen the attraction, but it seems that many, many other people do. The Sims was (and is) an extremely popular game, probably due to its real life (sort of) setting. The "Sims 2" just had to be popular as well. And it is - its sold more than a million copies in its first 10 days of availability. The new game expands on the game's virtual life environments by providing more complex characters, with more developed psychological and social dynamics.
"They have aspirations, memories, a much more detailed social landscape and knowledge of their social relationships with other Sims." - Will Wright, creator of the game.