3 feet was the standard a few decades ago, now a more comfortable distance is 42 inches.

We just finished a total kitchen remodel (search New Kitchen from Hell to Heaven) and we were concerned about the main traffic aisle from the side door through the kitchen. We made that 45" wide and made the space between the front counters and the island counter (where we do the majority of our prep work) 34". It works fine for us and makes everything very handy for work.