Having been raised in a family with a good number of older people who knew how to live beautifully, I can offer a bit of what I've observed in certain places around the U.S............
* In West Palm Beach, I saw retirees having fun, dressing up, going to lunches & dinners or shopping - enjoying the weather and other friends. WPB is a beautiful, sunny place to spend winters.
* In Scottsdale, I saw the exact same thing. I even had a house there myself for a dozen years. We lived around the pools, golf courses, tennis courts. I was younger than a lot of people, but I loved the sun and weather, the beauty and cleanliness. Also - the dollar went quite far, in other words, you got a whole lot of house for your money, compared to California.
* In the Tahoe area, there are trees, there is skiing, there is natural beauty, and it would be a good place to retire, but there isn't a heck of a lot to do, really.
* Manhattan is where our family has a co-op full floor apartment. It is fun and exhilarating being there, and across the street is the park. There are countless restaurants and things to do - parties to go to - people and activity. A great place to live - and weekends you can get invited to South or East Hampton. Not inexpensive living, but a lot of fun.
* Denver and the area around it - especially Boulder would be a lively, fun place to live - with plenty of stimulating people and diversity. I've spent a lot of time there and love it. You have skiing close by - but you have winter to deal with, which can be good or - not so good.
* The Bay Area - especially Palo Alto would be the best choice - IMHO. There is a lot to do, and interesting and diverse people to meet and pal around with. The weather is terrific. You can get to The City (SF), Napa, Tahoe, Carmel, Montecito, West L.A. fairly easily. The best thing is you can stay connected to your alma matter (or other groups) where you can do more than just play golf or swim, or go to lunch. The Bay Area offers so much stimulation and physical activity. This would be an ideal place to live and stay connected, not just sit back and watch life go by. I think it is vitally important for retirees to stay active and busy - healthy - happy.