1: Goldenrod City - The city in the center of it all. If one lives in this bustling metropolis, every other city is only minutes away. It's got a park up north, a day care center down south and a large ocean to the west.
Shopping is always an option and the radio tower provides nice reception to all of the favorite programs. The underground is even a nice hangout for trainers and a great place to hold battles in an urban setting. Not to mention the Magnet Rail for travel.
2: Olivine City - The ocean harbor, the salty air wafting through the air, the local affair. this is truly one of my favorite places in the region. One can eat at the diner, battle/train at the gym, climb the lighthouse, fish, or even just hang out at the beach to the west.
The locals always have nice things to say and the cruise ship will provide a nice means of travel and luxury. This place gives the very essence of the sea.
2: New Bark Town - A small, quaint town in separated from the world by forest and sea. A quiet place to relax and think, while taking a break from training. One can swim in the lake to the east, wander with in the forest to the west, or just lazily loiter in the middle of town.
I haven't mentioned any of the Pokemon in these areas, but I must say that they all appeal to my likes.
Goldenrod: Cute Pokemon can be found south (Ratata, Abra and even Ditto) and north (Growlithe, Psyduck and sometimes Yanma)
Olivine: Sea faring Pokemon west and south, and some nice normals up north (Miltank, Tauros and Snubbull for example).
New Bark: Forest Pokemon to the west (Pidgey Hoothoot, and Sentret) and some sea Pokemon the the east (Tentacool, Goldeen and farther out, Chinchou)