For a franchise game, my picks would be:
1st: Peafowls.
- They're cheap, and they bring in a ton of cash.
- In a moderate biome they won't need any expensive heating or cooling.
- They require a simple habitat that can fit in well at the entrance to a zoo.
2nd: Whatever I fancy at the time that fits in with the biome I choose and that has a high attraction rating to low cost ratio.
That way I'll have guests coming in to see the high attraction animal and consistent money coming in from the peafowls.
I'm sure there will be other combinations that make just as much sense, but I made a killing from my peafowls in the beta without even trying, so it makes sense to do the same again.