Kanto: Saffaron. It's close to Celadon, Lavender, Cerulian, and Vermillion so I could visit them without having to walk too far.
Johto: Violet City (Closest town to the part of Dark cave with Dunsparce in it), but Olivine, Goldenrod, and Blackthron would be good, too.
Hoenn: Lavaridge. Close to Wild Slugma, Flannery, And Hot Springs.
Orre: Phenec City. Rather live there than Agate or the Under.
Sevii Islands: Island four. Has Sneasel, Lorelei's house, and a Breeding center. Can't argue with that XD