Well, if we're to send a Generation Ship or Seed Ship to another system, it seems all we need is water, rock and energy to survive. We will have found some alternative to a magnetosphere,too, to protect us from those pesky waves and particles. A lush green planet is just a bonus.
Still, by the time we're in a position to do that, we'll have had plenty of experience living in domes* or caves on Mars so we'll know if spending your whole life in a giant Centre Parcs will drive you nuts or not.
*Buckminster Fuller on BBC's Horizon: