At Quartz, they have a map which shows which generic word men use most often to refer to other men -- as in saying, "Dude, what is that?" instead of the person's name.
"Dude" and "bro" are the most common in my neck of the woods, as studied by how often the words are used on Twitter. Others common across the country are "fella," "buddy," and "pal."
Not shown are the words "pally" or "pilgrim," both of which were used prior to the idea that one could express something worth expressing in 140 characters or less.