I have often hated Southern California because there is only one season, but the last time I visited I really enjoyed the mild weather. Old age, I guess. So San Diego would easily fit this criteria. But in general the problem with this question is unless you've lived there, it's based on a small sample size, frequently from vacation/holiday, so it's largely ignoring the negatives. Despite my affection for Texas, and how easy I would find it to live there, I can hardly pick one location over the rest because I know their faults well enough. So next on the list for me, after San Diego, would be Montreal, which I've only visited in Summer (although it was lovely).