No, I'm not a big fan of SF. My brother-in-law lives there and we've been about seven or eight times, the last time this summer. I don't find the locals particularly friendly and it is way too hilly. It's also expensive, but you can say that about a lot of California.
For me, nothing beats New York. As somebody once said "When you leave New York you ain't going anywhere"
EDIT: Honourable mentions for Seattle, San Diego and Boston (all good calls and I can see why people like them), but for me New York IS America.