I said Besaid, Luca, Calm Lands, and Omega Ruins

Besaid because it is a nice little place
Luca because movie/music spheres, main place for blitzball stuff, it's cool, and you get Auron back there!!!
Calm Lands because of CHOCOBOS!! Also it's just soooooo peaceful, and monster arena
Omega Ruins that place and Sin are the best place to build up stats later in the game.