I like Goldenrod City, it's right next to the breeding center and it has a long stretch of path that you can ride up and down to hatch your eggs faster.
I like blackthorn because of the dragon cave at the back (dratini line is one of my faves). I also like New bark town because I used to think the music was cute. Goldenrod is also a fave with me.
Like RosGOz said, Mauville is my favorite because of all the conveniences in it including breeding, lots of trainers, gambling, contests (Well that's in Vertreturf (or something like that) town, but it's only a 4 second bike ride away), and a long strech of land/ cycling road to hatch eggs fast.
I know I said my favourites were goldenrod and blackthorn. But if I was actually going to choose one to live in it would be the one with the treehouses. I think it would be fun!