Depends on what you're application is. A fatter tire gives more contact on a straight road. Drag bikes want more contact for faster accelleration. Cruisers usually have a fatter tire also for more stability. The narrower the tire profile, the less inertial to fight when throwing the bike from side to side in twisties or a road track.
My SV runs 120/60ZR17's in the front and 160/60ZR17's in the rear.
a GSXR's run 120/70ZR17's in the front and 180/55ZR17's in the rear.
There are limits with the forks / swing arms and brakes on how wide a tire you can run. If you want some of the more technical guys to help out, we need to know your bike, stock tire size, and what you want to modifiy the bike for.