Yeah, you're going all over the map Soulseeker.
The whole west coast has earthquakes. I'd stick with NYC if you've always wanted to live there. Live where you want to live. Not where magazine editors/ real estate brokers say you should.
Chelsea is the "official" gay neighborhood of NYC and East Village is nice also. Manhattan rents though are high below 125th Street. Even Harlem is starting to get expensive. You'll definitely need roomates if you decide to rent in Manhattan, you can thank Sex and the City for making every single woman want to move to Manhattan and driving up rents for the rest of us.
Brooklyn is a great place to live and despite all the hipsters doesn't have Manhattan's price tag (yet). It's a good alternative to Manhattan. Brooklyn Heights is very nice but a bit on the expensive side. I'm looking in Park Slope and Carrol Gardens as they are nice and more affordable area. You can also check out Jersey, NYC's unofficial "6th borough." Namely Jersey City and Hoboken.
You should really have no problem finding like minded gay guys in any of the five boroughs as NYC is a gay "mecca" city. Possible the gay mecca of the nation.
If your income is $100,000 than a single person can live well off of that, even in New York. You should take a look at the
City Data and
Wired New York forums. Lots of helpful info there.