The difference was expectations. The Sims billed itself as a life simulation game, and as such it was a very fun one. Spore claimed to be a revolutionary worldchanging game. People called it the Citizen Kane of games. It was the end-all be-all to the history of gaming, the game that did it all. Turns out it was just a lifesim game, and a lot of people who thought they were playing the best game ever stopped playing within a day. I know I did, and I'm still a bit mad at Will Wright for that.