Steve is right, a lot of good ones to choose from, can you narrow down the kind of cuisine your into. For starters, one that I recommend to many people who have a universal pallet is Curly's in Lackawanna.
If you like a good chicken wing Duffs or Anchor bar are pretty good.
If youre looking for breakfast I highly recommend JJs Cafe on kenmore, its run by a local family who are very friendly and make excellent food on the cheap. Cant recommend it enough.
Anywhere on Chippewa St....Soho, Chocolate Bar, Bada Bing, Frankie Primo's, Patina 250, The Local.
Best burgers are at Allen St Burger Venture and best BBQ at Fat Bob's on Virginia Place.
The Left Bank is superb. I am also partial to The Billy Club, great choice of bourbon and bartenders who actually know how to make a drink. Marble & Rye, Tappo, Sea Bar and Toutant are over by Shea's are are fantastic.