According to David Emery of About: Urban Legends and Folklore and DogsInTheNews.com:
This dog Hercules, purported in emails circulating around the Internet, to be the World’s Biggest Dog, is actually…
a hoax!
In fact, no living dog has, as yet, beat the gargantuan size of the real Hercules, who since 2001 has had that distinction.
Read more at The Scoop from DogsInTheNews.com.