Though I love playing with favorites, whenever I'm starting a new game, whether it's in a new region or not, I always use Pokémon native to that region up to the Elite Four. I always love trying out new Pokémon, so if I have the opportunity to do so, I'll take it! Typically after I finish the game, I'll throw in some if my favorites from previous games/generations and the current game and make a team out of them. There has been ocassional times where I have a whole team of new Pokémon, and times where I had no new Pokémon. It all really depends. :P