Which has been the highest grossing Hollywood film of all time?

It’s Avatar. Earlier this record was with Titanic. It took 41 days to Avatar to overtake Titanic to become the highest-grossing movie ever at the worldwide box office at $1.859 billion ($555 million domestic plus $1.304 billion foreign), compared to Titanic's $1.843 billion. The science epic film written and directed by James Cameron and starring Sam Worthington, Zoe Saldana, Sigourney Weaver, Michelle Rodriguez and Stephen Lang is a fictional story set in year 2154, when humans are mining a precious mineral called unobtanium on the lush moon Pandora in the Alpha Centauri star system. The colonists' expansion threatens the continued existence of the Na'vi—a race of humanoids who are indigenous to Pandora—as well as the moon's ecosystem.