BEST KOSHER RESTAURANTS NYC
You'll probably want to post over on the Kosher board for more knowledgeable recs.
That said, I agree that the Kosher places in "Curry Hill" are good. I've enjoyed many meals over there.
There are also several Kosher restaurants on the Upper West Side, though I've not been to any of them (Darna, Talia's, Mike's, etc.).
I did look on menupages.com and there is a "kosher" category. That might be a place to start for you.
I don't know either first-hand, but there's Le Marais for steak and Colbeh for Persian kebabs. I also haven't been to Buddha Bodai in Chinatown (they also have one in Queens), but they're kosher vegan Chinese. As has been mentioned there's a bunch of South Indian veg/dairy with kosher certification. On 47th Street, in the Diamond District, there are two fun choices: Diamond Dairy, right in the jeweler's exchange, is one of the last of the classic NY Jewish dairy restaurants, and also on the block is Taam Tov, a Bukharan place--might be something you can't get in France since the community is basically based in Israel & NY--both of those would be lunch only. Rectangles on the Upper East Side is a great bet for Israeli-Yemenite. They have stuff like malawach and shakshuka, plus falafels etc.
If you plan to go to the outer boroughs there are other choices.
5 Mott St, New York, NY 10013
150 W 46th St, New York, NY 10036
43 W 39th St, New York, NY 10018
My observant friends like Wolf & Lamb a lot for steak and burgers. Since I don't eat steak or burgers, I can only tell you that the fries are pretty good. And for $8, they oughta be.
On the Lower East Side, there's Noah's Ark. It's very close to my house, but I haven't eaten there because the prices offend me deeply.
re: small h
I just looked at the Noah's Ark menu. I don't know why the prices offend you. For a kosher restaurant the entrees aren't that high, and deli sandwich prices are in line with Sarge's, lower than 2nd Ave. Deli. One always pays a premium at kosher restaurants that serve meat.
399 Grand St, New York, NY 10002