Really haven't travelled extensively enough throughout north America to make a detailed list...This one is pretty much based on my jerk reactions of how fun I found each city based mostly on extremely limited visits and places where I could see myself living.
1. Northwest Portland, Oregon - I really have yet to find a place I would want to live more than my hometown (though I grew up in the burbs). It's green spaces are what I would miss most if I left...I mean really there are at least a dozen parks within walking or very short driving distance away from my house, and I don't mean tiny patches of grass that you find in southern California, I mean parks at least an acre in size but typically much larger with forest area, swamps, streams (large enough for my dogs to swim in). It has an awesome and accessible downtown, wine country, the mountain, the gorge, the beach within an easy drive....ideal...clean...everything I could really want.
2. South bay area of Los Angeles, California - If there's one place that might unseat Portland as the place I'd want to live it might be L.A. It's truly unlike any other place I've been. I live here now as a student, so my opportunities to actually get out and really know L.A. well have been extremely limited, but I like what I see. In the line of work I plan to enter I would not make enough money to live in the nicer parts of L.A. County so we'll see where I end up. Also, there's the crowds and lack of green space that I previously mentioned. Taxes are high, and the transportation sucks, but I still think that if L.A. had the public transportation infrastructure that New York had it could be the greatest city in the world.
3. Anywhere in the San Francisco bay area - Probably the most beautiful major city I have yet to see. Have never had a bad time in San Fran and I even liked the Silicon Valley area a lot when I drove through. It has fantastic weather and a high quality of life. I could easily be happy living anywhere in the area.
4. New York City, New York - No explanation needed. I definitely want to spend
some time there, but I have yet to decide if it's a place I could live for my entire life.
5. Seattle, Washington - I love Seattle for the same reasons I love Portland, but considering the roots I have in Portland, I probably wouldn't live in Seattle unless I had some amazing job opportunity; however, the career I will be pursuing in the near future wouldn't allow for that.
6. Washington, DC - Absolutely loved it when I stayed there a few years back, granted a large part of the reason I loved it so had to do with the fact that I stayed with friends in a
stellar row-house on the hill with a roof deck and view of the Capitol building. The subway and fast pace of the city also appeal to me, and in all honestly I will probably be living in D.C. for a good many years for my career.
7. San Diego, California - I have had only one brief visit to San Diego, but I liked what I saw. Love the climate, culture, and amenities but again, considering its extreme proximity to L.A. the only reason I'd live there would be some great job opportunity.
8. Vancouver, British Columbia - Competes with San Francisco as the most beautiful city I've ever seen. It scored lower on the list only because it's in Canada and I probably wouldn't live outside the U.S. unless I were working at the American Consulate there.
9. Las Vegas, Nevada - I would never live in Sin City let me say that now, but I will return again and again when I need to escape my life for some heathen fun.
These are really the only cities I have spent enough time in to develop mature opinions on. I have been to New Orleans and frankly, I won't be returning for at least a decade. I was in Boston for a week and I'm sure I would like it a lot more if I returned, but it didn't seem all that unique or exciting to me at the time.
Cities I would love to visit soon: Miami, Honolulu, Montreal, Toronto, Chicago, Denver, Austin.