I think most New Yorkers would agree with me that the Chrysler Building is the best-looking one in the city. The number of non-traditional, post-WWI (in both chronology and spirit) public buildings that can be described as beautiful is very small. The Chrysler is the most elegant of them that I've seen.
I would put downtown's Municipal Building next. It was finished in 1912 and may or may not have served as the inspiration for Stalin's Seven Sisters in Moscow. One weird thing about this building is that it's more impressive up close than from a distance and not at all impressive from the inside.
The NY Public Library's main branch, number three on my list, looks much better from the inside than from the outside, though the exterior isn't ugly either. Of course Europe is full of such buildings, which you can't say about the Chrysler, hence Chrysler's place up top.
The Woolworth is fourth on my list. It's hard to go wrong by imitating Gothic cathedrals, so you can't give it too many points for originality either. However, it looks a thousand times better than the Sears Tower and about a million times better than anything Wal-Mart would have come up with if it ever entered the field of monumental architecture.
The Empire State. Like almost all skyscrapers it looks better from afar than when you're standing right under it.
The Met Life complex on 23rd Street. The bell tower was built in 1909. The main building was supposed to be 100 stories tall, but was cut down to 30 in the middle of the Great Depression. Amazingly, it doesn't look stubby as a result. I was once rejected for a very good job inside the old Met Life complex, and yet I still love it.
The New York Life Building. Same idea as with the Woolworth, but with a more solid and reassuring feel, because it was built by an insurance company.