consider the plot, character, and pokemon development in your choice. speak to the strength of the pokemon in that region and those of the main characters. talk about the rivals in each region and how interesting the battles were in the region you choose. also consider the bad guys in each region (rocket, magma, aqua, galactic, plasma), how evil they were, and their stories. most importantly consider how strong ash was in the region as well. in my opinion, he was at his strongest in sinnoh because he had probably the best team when he challenged the sinnoh league compared to his other league appearances. dawn's story as the daughter of a top coordinator is awe inspiring and her future remains to be seen after she loses the grand festival, but one can assume it will be good. another thing is that paul is probably ash's best rival because they differ in every way and the battles between them were intense. finally, team galactic's plot was by far the most evil, they were going to destroy the world in favor of a new one. what do you think? (im throwing battle frontier and orange islands into kanto, because thats where they were)