I believe the Nephilim were the Titans of Greek mythology.
I agree. Webster's Dictionary has titan (from Greek) = any of a race of giant deities, titanic = of great size, strength or power, and titanism = rebellion against established order. Fits nicely with the Biblical description of the Nephilim.
Oops! Hercules was a demi-god, the son of Zeus and a human mother, so yes, he would be comparable to the Nephilim. And Zeus would be one of the fallen sons of God. He certainly had a lot of lust for the daughters of men.
"I believe the Nephilim were the Titans of Greek mythology."
Or, could they be from Numenor?