The answer is relative to the site's purpose.
Google is ranked #1 and gets about 1,470,000,000 visits a day.
Facebook is ranked #2 and gets around 952,000,000 per day.
Amazon #3 at 153,000,000 per day.
WebmasterWorld is ranked 672 with an estimated 1,863,839 per day.
Ranking as per Alexa.