I depends greatly on which civ you´re playing as well. Arid hot new world is perfect for Amanitore, for example. Peter would fare a lot less well..
In my experience, There are two tough scenarios when dealing with AI:
- The above mentioned "Crowded Island", where you simply get beat by AI cause they start with extra settlers. So you don't have room to build cities and will fall behind quickly
- Underpopulated pangea, where AI settles all over the place, and keeps spamming 'don't settle near me' messages until you are a warmonger, despite not starting a single fight.*
*I must say, my current pangea game, Mapuche has a swath of land in his backyard which is not being touched by anybody, despite the many resources, hills, rivers, etc. It's almost as if a hard city cap was introduced recently...