Note - I grew up in Westchester and frequently eat out. I've occasionally checked out the site, and found it useful, so I thought I'd try to be useful myself and offer my opinions, positive and negative. Of course, if I have a bad experience the first time, I tend not to go back, whenever possible, so that bad experience might have been a fluke.
American/Continental/Other: Cafe Meze in Hartsdale. Mighty Joe Young's in Hartsdale. Umami in Croton has eclectic and delicious food at reasonable prices, but its no-reservation policy can mean long waits. Upon being told of one such delay, we went to Dudley's in Ossining, which was nearly empty (one other table was occupied). The food was good, the service surprisingly slow at first, and the former speakeasy is interesting to explore (a trap door behind the bar leads to a tunnel that once went to the Hudson). I hope the place isn't always empty. They offer jazz on some nights.
Bakeries: Jean-Jacques (Millwood, Croton, Pleasantville) offers some good soups, salads, and sandwiches. Desserts are way too sweet. La Parisienne, a Japanese bakery in Hartsdale, has the best almond and chocolate croissants (not much competition in Westchester), and tasty desserts. Good bread is much easier to find in the city, so I sometimes settle for Eli's from a supermarket. Turco's raisin-walnut bread is good if it's fresh.
Burmese: Mingala in Manhattan was excellent in the past, better than the Burmese food I had in Burma (Myanmar), but the food disappointed the last time.
Chinese: No favorites in Westchester. I've tried most of the ones people recommend (David's Jade Palace, Hunan Ritz, etc.) and haven't been impressed. Next up: P.F. Chang's. In Manhattan, Shun Lee is excellent. I've never been to China, so in my experience Tokyo has the best Chinese food (Hokkaien).
French: La Panatiere in Rye is my favorite. Except for one occasion when the food was merely OK, the food, service, and setting have been delightful.
Greek: The food at Lefteris Gyro in Tarrytown hardly compares to Molyvos in Manhattan. Someone recommended the Greek diner on 119, near the entrance to 287, so I'll try that sometime soon.
Italian: No favorite pizzerias, although I live (and eat) in constant hope. The Horseman diner in Sleepy Hollow has a decent (if not traditional NY) pizza special on Mondays. Its (Greek) owner once owned a pizzeria. As for fancier Italian, I like Mulino's in White Plains, although service is slow for my taste. Terra Rustica in Briarcliff is better than its sister, Rustico in Edgemont. The casual Pasta Paese(?) in Briarcliff has good pasta (not pizza). I was disappointed in Amalfi's, but look forward to trying Torchia's. Sapori d'Italia in Ossining has good gelato.
Indian: Bengal Tiger in White Plains was the first place I ever ate Indian food and is still one of my favorites. Malabar Hill in Elmsford and Royal India Palace in Yonkers are also good. I'd like to try Nyauta's in Yonkers. I've been to India, but the best Indian food I've had has been in London and Tokyo. The Bombay Club in Washington, D.C. has great food and service in an elegant setting.
Japanese: Tsuru on Central Avenue, and Toryanse in White Plains are my favorite all-around Japanese restaurants. Tanto in Eastchester has take-out sushi (order ahead if possible, instead of getting it out of the case) and bakery goods. Azuma-sushi (sushi) in Hartsdale is an old favorite, alhough it's been a while since I've been there. Ichi Riki has had horrible, past expiration food whenever I've been there, and both my dining companion and I (both Japanese) vowed never to eat there again after the last time. Nevertheless, I know people (not Japanese) who love it. In the steakhouse department, Noda's edges out Gasho, although neither is particularly good. At Gasho, try not to be seated so that the smoke constantly wafts into your eyes. In Manhatttan, Hana-sushi is a sentimental favorite.
Mexican/Tex-Mex: No favorites. Lots of people seem to like Santa Fe in Tarrytown, but I'm not one.
Portuguese/Brazilian: No favorites. The food at Caravela in Tarrytown is one dining companion's favorite, but for me it's nothing to the real thing.
Thai: The Thais in Ardsley and Sleepy Hollow are hit-and-miss. Siam Orchid in Edgemont and the Thai in Mamaroneck are more reliable. Of course, the best Thai is in Thailand.
Turkish: Turquoise in Mamaroneck is superior to its sister Turkish Meze in food, service, decor (and price). The best Turkish I've had was in Auckland.
Vietnamese: No Vietnamese restaurants in Westchester. The one in Poughkeepsie (I don't know if it's still open) had decent food, but I was violently sick after eating it. I don't know if there was a connection, but I don't plan on going there again.
Views/Special occasion: My favorite special occasion restaurants are La Panatiere, Mulino's, and Cafe Meze. None of the river restaurants (Blu and Harvest on Hudson in Hastings, Rudy's Beau Rivage and Charthouse in Dobbs Ferry) has particularly good food, in my experience. Equus in Tarrytown gets top ratings, but the food and service didn't deserve them when I went. The setting, however, is terrific. Other special-occasion restaurants that I'm not in a rush to go back to are Maison Lafite in Briarcliff (gorgeous setting, below-par food), Crabtree Kittle House in Chappaqua (ditto, although many people feel differently), and Auberge Argenteuil in Hartsdale (beautiful outdoors, but a musty, unpleasant smell inside, although I haven't been there since the management changed).