Visited all over the States, been to some good and not so good citys over the last 30 years, and visited most of the major citys and what would be big must see's, but I would recommend getting out to see some of the country outside really built up areas.
Wyoming, Montana and Colorado, spent weeks in each state just travelling around are fantastic to see. Maybe stay on a working ranch (not a dude/Disney type place).
I did like Washington DC, and even went into the White House which was very interesting, but this was about 25 years ago. Hated NY with a passion.
I prefer the smaller places outside SF, like Carmel, Salsulito and so on.
Went back to Boston about 7 years ago after a break of almost 18 years and really did not like it at all. But there are some very nice areas of the whole of New England which is made up of many states to see.
My idea of hell would be Disney in Florida! So we all like different things and your going to get really conflicting advice depending on what we all like