[Poopsi]

My personal favorite is Europia, with a limited number of Pretenders. It´s medium sized, not so small as to limit the lenght of your games severely, but not so big as to make every turn last ten or more minutes (as long as you keep a rational number of pretenders on board). As an adittional bonus, the geography roughly mimics Europe's, and the historically-inspired nations (Ctis, Pythium, Ermor, Marignon...) are in their places. So you can rp fantahistory if you like.
Personally I like to add extra starting points. For instance, I give Ryleh a position in the atlantic, and Atlantis in "Kingdom of the Deep". Adittionaly, I gave Machaka another province south of Morocco.

Closely followed by "Realm of the Gods" (sp? the big one. 300, or 500 provinces.) if I am willing to put up with the turn times.