As so many others here have said, "It depends."
I may well say, "Whazzup, dude?" or "YO!" to my teenage grandsons (15 and 19 years of age), and I might say, "Whazzup?" or "Whatcha doin'?" to my daughters.
For my grand-daughters (ages 10 and 4) "Hi, Sweetie" is more likely.
If the phone has been ringing off the hook, I might well answer with, "Grand Central, go ahead!" Or, if caller ID shows one of my kids, "It's your nickel...." Otherwise, the standard, "Hello?" will do.
On HP commenters, if they are a new commenter, "Hello, (user name)," or, if they've commented on several of my hubs, "Hi, (user name--or shortened version)," or "Hello again,..." or "Hi, there..."
Like I said, I match my language and usage to the audience...including the use of vernacular slang with the appropriate audience. I am equally capable of language befitting a conversation with the President or the Queen, or with a crowd of rowdy sailors or stagehands, noted for their 'salty' language....
In other words, I can fit in anywhere! ;-)