I've been to a great many places but not many make me pine to go back to to the point where I would miss out if I didn't. Plus there are so many places I'd like to see, that it's often tough to want to go back to the familiar travel spot when I could experience something new. Usually it's only to let someone else experience what I've been able to and share it.
Like a few have said, London is one of those places but I feel so comfortable there, it is a little like going, not home, but back to a place that used to be home. Thanksfully I'm there 3-5 times a year so the itch is regularly scratched.
Cape Town is another one of those places where I feel instantly at home and do pine to go back to. My wife's South African, so I will certainly be back every once in a while. Again, like London less of a holiday destination and more of a homecoming despite never living there for more than a few months.
Bali would fit the list as would Martinique. Newfoundland certainly. Napa too. Grenada (and southern spain in general) most certainly. M wife won't let me take her to the South Pacific for fears I'll get more tattoos but I'd like to show here Fiji and Vanuatu.