Man, sim games have gotten complex. Remember the original SimCity? It was a lot of fun. It took a couple of hours to figure out the simulation rules, but then you could do most anything with the game. I got bored of it then.
Contemporary simulation games are much more complex. The Sims 2 has an enormous amount of depth, complex social interactions and detailed dollhouse environments. And the Roller Coaster Tycoon 3 demo just blew my mind. Simulations of everything from your total park finances down to the details of what colour balloons your peeps are holding in their hands and how much extra for onions on the hot dogs.
The problem with all this complexity is it can be opaque and frustrating. Good sim games expose details of the simulation without revealing too much of how it works. SimCity 4 failed for me; despite reading the strategy guide and various websites I never could figure out the correlation between choices I made and what happened to my city.
The Sims 2 has a different take on this problem by making it basically OK to do anything. Yeah, it might be hard to make your Sim the smartest professor who gets the most woohoo, but you can have fun anyway just stumbling along and making him wet himself in front of guests. I can't tell from the RCT3 demo whether they've got the right balance of complexity and approachability, and the interface is awfully complex, about 100 screens. Sure is pretty though.