Maxis has quite a record in providing interesting simulation games since they came out with SimCity. The game SimLife: The Genetic Playground, however, never became a hit. In the game you can simulate an ecosystem including a climate simulation, a plant groth model and a complex model of animals including herbivores (plant eaters), carnivores (meat eaters), and filter feeders. Not enough, they added an evolution model including genes and phenotypes for all plants and animals.
At this point it becomes clear why this game was without success: it is more a research simulation than an actual game. The number of statistics and graphs also support this impression. Moreover, I guess that the actual processing power at the beginning of the nineties did not allow for extensive simulation experiments. Another distinctive feature between a game and a scientific experiment: a game is designed to give the player a fair chance of success (at least in the lower level). In contrast, SimLife simulations tend to end up in extinct animals and low-diversity flora very often. For example, Spore (from Electronic Arts, which bought Maxis some time ago) has a similar scenario, but is designed as a game. I was not really able to create a stable ecology with more than 5 different species, but still I prefer SimLife over Spore.
In overall, SimLife is interesting from a complex systems point of view even still today. If you want to try it, find it at some abandonware site and run it using an emulator, e.g. dosbox.