I think it would be really fun to do a type of Virtual Villagers set on another planet in space. Like the people have to escape earth because of some catastrophe, so they just shoot off into space, and this is where the few that survived landed. It could have some interaction with intelligent life on the planet, terraforming perhaps, finding a source of water, etc.

The breeding games (Fish Tycoon, Plant Tycoon) could also be branched into other areas, like "Canine Tycoon" (which could be lots of fun, because the parentage could be set up so that you could have some idea of the traits being given to the puppies, just like with real dog breeding) or any other animal that has lots of variants. You could actually do something like "Petri Tycoon" where you breed and combine various bacteria for beneficial (or not so) activity.