My clearly unbiased (

) vote goes to the Northeast.
I've been to every single one of the cities OP mentioned except San Diego, and here are my brief opinions on each:
Seattle: Very friendly, seems smaller than it actually is, emphasis on technology.
Portland: Extremely environmentally friendly but small- I think I'd get bored living there.
SF: Best of the bunch. Has a little bit of everything, really. I'd be very happy to live there.
San Jose: Might as well be SF as it's just a drive away.
LA: Is decent. Seems like it's only good if you're somehow involved w/the entertainment industry. Everything is annoyingly far apart.
Vegas: Would never live there. Great weather, but literally nothing to do if you're not a tourist.
And here are my biased opinions on Northeastern cities:
Boston: Amazing.
NYC: Amazing.
Philly: Pretty great.
DC: Amazing.