More like a Sim Life or something.
It's interesting because the game engine interpolates how a creature would move. The game starts out very focused, with you being a simple creature trying to survive...and once you "lay an egg" or something, you can evolve your creature. Eventually you can evolve them to the state of sentience, and all the design and animation is not done by a team of artists, but buy the game design itself.
Eventually you'll enter a more "civ" like nature of the game, and it seems that once the game is "done" you can always zoom out a bit more.
For instance, you start just in the water, but then you zoom out and include land. Then you start to create a culture with diplomacy and military and whatnot where you zoom out continent/planet wise. And once you've accomplished "enough," you can zoom out to the solar system, and colonize other planets and whatnot. Finally, you can zoom out to the galaxy view, and use your technology in a SETI radio wave style to find other intelligent life in the galaxy. Providing you have interstellar travel, you can then go and travel to them. Will Wright's demo did this, and it showed him having a blobular UFO type design (of his own custom design) heading to the new planet. He freaked them out and they fired at him, and he showed off a "War of the World" type scene where his technology was too powerful and he blasted the distant civilization with death beams as missiles bounced off of it.
The Sim City reference was more in the way the game "plays" so to speak. Describing Sim City doesn't exactly make it sound like a fun game (You just manage a city), and I think Spore is the same way (although I think Spore sounds like a lot of fun to play).
It's something you might enjoy along the lines of unit customization. You can customize your species just the way you want it, and how they progress. I believe his sentient species was a three legged creature of some sort.