Irvin's, near Great World at the intersection of River Valley & Zion is pretty good. Boon Tong Kee (famous chicken rice place) is a hundred meters or so further up River Valley.
Obvious tourist bets? No Signboard, Jumbo, Newton
Best bet? Get in a taxi. Any taxi. Ask the driver about his favorite. If he gives you any answer other than Newton, check it out. Find out where the locals go, get yourself pack of tissues, wear a shirt you don't care about, "chope" a table, pop open a Tiger and enjoy!
Can, lah!