Kanto - original and simple. the region that most regions is based of. for me words cant describe the region.

Johto - it is so rich with inspiring traditions, making the one playing it feel like he/she is the chosen one some sort like that. the first region that introduces legendary pokemon like a god. and this is where the best battle for me takes place (red vs. ethan aka gold)

Hoenn - the best region for me. it was a region full of firsts just right after kanto, since johto is some sort of still stuck with the kanto region (one pokemon league,and it is beside kanto). first time to see two teams fighting each other (t.aqua and t. magma). as the best sets of legandaries for me. The largest battle frontier can be found in the region.

Sinnoh - best legendary pokemon story for me (arceus=creator, such a big revelation). it makes me feel like im in a country that has a cold climate. hottest champion (pls. im not a maniac here).

Unova - for me it has the most interactive gym leaders in it since they are like guiding you through out the whole game especially the team plasma castle arc. great story too. and the chance to battle against other region's gym leaders, and champions is such a bad ass idea, it makes this region battle focused. team plasma is unique compared to other region's teams, it makes me feel that they are ancient since they make use of knight suits and castles.

Kalos - i haven't played x and y yet. i cant tell about something i haven't experienced yet. so sorry to all kalos lovers there.