Personally, my heart goes out to Anistar city. The giant Sundial, the Psychic Gym leader (heck yeah, Olympia! You go girl!), the mystery around the old man's death, and I especially adore the BGM. But what I'm more interested in is what you all consider to be your favourite town or city. And why do you like that town/city so much?
Sootopolis city. I love the feel of the city, and the music is so upbeat and nice! It deals heavily with legends and lore and I find that really fascinating. Also it has my favorite character in it but thats beside the point. I love the city as it feels really unique from the rest of Hoenn. It just brings up so many questions about if the city has a different culture from the region in my mind. It's truly an amazing city.
Goldenrod is a Gen 2 City. Whitney and her Miltank roam the city looking for those they can flatten with Roll Out. I have a fondness for Sunnyshore and Lilycove City, both are next to the sea and I adore the sea.
Always gonna be a fan of Snowbelle City from X and Y, as well as Snowpoint City from Diamond/Pearl/Platinum. I'm a sucker for snow themed areas.
Yeah, it is usually the bane of Johto Players as Whitney's gym is there. She is famous for killing Nuzlockes.
Sootopolis and Mossdeep in Hoenn are some of my favorites. I love how aquatic the landscapes are in Sootopolis, having a giant crater of water (that is crystal clear and reflects the stars at night) sealed within the city with beautiful white rock. There is also a garden in the city and pretty waterfalls too. Mossdeep is cool because half the city is a giant puddle and the rest is connected to the space center. When I first played Sapphire I loved just running around on the water covered sand and fish on the shore for fun.