I hear that the new restaurant in the Trump tower, Sixteen, has the finest views in the city. I have not been there myself yet, but know folks that have and it's the first thing they mention when you ask them about their experience.
If you want to do a casual cocktail type pre-dinner or post-dinner stop with a view, I love the roof garden at NoMi.
Even though it's very "touristy" the views from the cocktail lounge at the top of the Hancock are stellar. Take the elevators to the Signature Room, head to the NW side of the building and you're all set. I take out of town clients there and they are always floored- make sure it's not cloudy outside.