If you like Japanese/Asian fusion food you HAVE to go to Koi at the Bryant Park Hotel (it's at Bryant Park and W40th St, so only a few blocks from TImes Square).
The food is exceptional and not over priced for NYC. The architecture inside is breathtaking and there's a great beer-cellar style bar downstairs. Plus Bryant Park itelf is a beautiful little square so it'll be a romantic night out. You can order a proper main course or else a few smaller dishes or sushi. The kobe beef potstickers (Asian dumplings) are beautiful and they do a great softshell crab too. They have more orthodox dishes like tuna and salmon too though. I try to go every time I'm in New York.
If you want something a bit more tradtional then Pastis in the Meatpacking District is a great spot. As the name suggests it's French-angled food but is ever popular - http://www.pastisny.com/
For somewhere off the beaten track try La Esquina, a Mexican place that looks like a taco stand from the street. That's because it is. But if you've booked, or you've timed it right, there will be a woman by an internal door who will show you downstairs and through the kitchen into a little restaurant/bar that does great food - http://esquinanyc.com/
With any of them, the sooner you can book the better. I guess it'll depend on what you're after and what you want to spend though. Give me more details and I'll give you more ideas!
If you're looking at a decent budget (say £100 for the two of you) then you should be ok for any of those places. It'd have to be Koi for me though - http://www.koirestau...rk/galleries/1/
Give me a holler if you want any tips on clubs or bars etc too.