My prediction is that it will start small, like The Sims. I remember seeing the game come out way back when and asking myself "who will play this for very long?" But it happened to hit the cord that is common amongst many, many people... building alter-ego's. People could create THEMSELVES. They could also create who they wanted to be. This is an undeniable aspect of the Sims series. They are more than just life simulations, this is YOU. This is why it resounded so heavily in the mainstream and even some of us hardcore gamers snuck into our rooms and tried to make our Sims succeed. And, let's face it, many of our girlfriends/wives wouldn't have touched a PC if it weren't for The Sims.
It is an example of the perfect gameplay mechanic. I found it a bit monotonous, but it was addictive on a personal level. We owe a lot to The Sims for bringing such a simple and mundane gameplay factor to bear against the millions and millions of casual gamers (some of which subsequently turned to hardcore gamers).
Spore, on the other hand, will probably not be as impactful as The Sims, but it will have a more immediate following. The question is, can it deliver? We don't know that yet. Right now, it seems highly accessible. If a girl wants to sit down and just create species of animals, she can do so. If the hardcore gamers wants to go from cell to galactic God, he can do so. If the relaxation-based gamer wants to take a trip around the local cluster in search of new creatures, he can do so. The gamble here is just as the article pointed out... there's really no one gameplay element, no relatable overarching goal. Discovering the Solar System in Spore has nothing to do with how much money you'll have when you get your next promotion. And it's going to be up to the freshness factor of Spore to take these quasi-gamers raised on The Sims and introduce them to varied, unrelated gameplay and let them run with it.
WW is banking on two factors here. He's mentioned this many times in his talks. He noticed that playing the Sims was different than creating in The Sims. Many people (women/children included) loved to make new Sims, houses, assets. But The Sims lacked the ability to effectively SHARE those assets. WW is predicting that the creative side of Spore (90 percent of the gameplay instead of a supplemental add in) will capture the minds of Sims players. He's also hoping to keep them there by building in ways to easily access the content of other people. He saw the community around The Sims, not the success of the game itself, and is running with the elements to boost the social aspect of the game and make it easier to do so.
Again, the question remains... does Spore have the power to hold gamers until the point where they have created a few creatures and encountered a few more (and actually realize it). I feel that some will be overwhelmed by the potential complexity of the game and I pray that the game will be as seamless as possible between phases. I was initially opposed to the "choose a stage" option, but they were smart to do this. Many women/children could care less about the tribal/city/civ stages of the game and would focus exclusively on the Create/Space phases.
If the components match up right, Spore will be a creative Swiss Army Knife. Everyone will find something to immerse themselves in while putting in minimal administrative effort to customize the content in their games. The Massive Single Player paradigm is going to work very well for the introverted and the non-competitive (again, most women/children).
It may be cartooney and light-hearted, but I think this is an evolution of past experience. Count the number of people who played SimCity compared the SimEarth and those who played SimAnt to SimLife. I'm hoping, however, that there will be the ability to alter some of the gameplay to make it more cutthroat or more realistic (I could care less about the cartooney nature... I like Viva Pinata, so). I also hope there is more and varied drive introduced into the space phase so those explorers (which many will wind up being) will not run out of new things to do.
Long story short, Spore will start out with a bigger bang than The Sims, but it's in the air exactly if an uncontrollable reaction will be initiated. We'll see in about 6 months.