I think you need to be more descriptive about what you're looking for than just "romantic."

Are you looking for big or small? Exorbitant or reasonable? French, Italian, American, or something else? Do you want something fancy and famous or hip and obscure? Do you want the restuarants where the law firm partners and i-banking managing directors eat? Or the restaurants where the associates and analysts eat?

I'm a fan of Nook, a tiny (5 or 6 tables, can't fit more than 15 or 20 people in the whole place) Polish-influenced new-American restaurant on 9th Ave between 50th and 51st. I think they raised their prices recently, but the food is very tasty and it's still a great value compared to most of the other places mentioned here. It's also BYOB, so you can bring a nice bottle of wine and not have to pay a big markup. Service is not overwhelming, since it's just one guy (Konrad, the owner) holding the place down. But he's a nice guy, and I really like the place's vibe.

In addition to Zagat's, check out the restaurant listings on newyorkmetro.com/restaurants. Also newyork.citysearch.com. Remember that Zagat's is just a compilation of surveys, while sites like newyorkmetro (which is run by New York Magazine) have actual reviews written by food critics. Some folks prefer Zagat's less-subjective approach, but I kind of like reading descriptions in prose rather than just numerical scores accompanied by a few pull-quotes.

In the newyorkmetro restaurant finder (on the right side of the page) you can search for restaurants by things like neighborhood and "special feature" (which includes "romantic"). I've found their "romantic" rating to be hit-or-miss, though. For things like "romanticness" I think Zagat's survey approach is probably a better bet.

Also, for reasonably priced, cozier, hipper romantic places (as opposed to big-fancy romantic places), I find that the Village (Greenwich and West, more than East) usually has much more to offer than midtown. Look for little restaurants like Home (where I proposed) and Deborah. But it really depends on your idea of romantic.

Oh, and if you want the all-out superior food and service with no budget restrictions experience, there are a bunch of new places in the Time Warner Center that are virtually guaranteed to break the bank (and impress). And there are always top-notch places like Grammercy Tavern and Union Square Cafe a bit further downtown.